A related topic is whether we could recognise some former T-sites that are of OUV and were removed nonetheless for various reasons. Some of them have already been discussed at this forum.
Examples:
Afghanistan - Ai Khanoum?
Argentina - Las Parinas (appears as a gap at a thematic study about volcanoes)
Belarus - Minsk (Communist architecture)
Colombia - natural sites
Costa Rica - Guayalbo (a major representation of Ishtmo-Colombian area)
Eritrea - Adulis, Matara?
Germany - Walhalla?, Bayreuth Festspielhaus (extension?)
Greece - Akrotiri at Santorini (one of the most significant Minoan sites with frescoes and town layout surviving intact)
Guyana - Kaieteur
Hungary - Budapest synagogues (extension?)
Jamaica - Spanish Town?
Mexico - Bonampak (best example of Precolumbian murals)
Pakistan - natural sites
Russia - Yenissei bridge (now dismantled)
Turkey - natural sites
UK - Cambrige (representative of the Classical university towns), Manchester (industrial revolution sites)
USA - Chicago School, Big Bend NP, Arches NP, Sequoia NP, Edison N historic site, Savannah, Death Valley NP
Venezuela - natural sites

There are not many sites with potential OUV: Chicago School of Architecture, Cambridge, Akrotiri, a few natural sites?
But I would take this as an indication that the countries did a good job when revising their T-list. And when we criticize the European countries for the overrepresentation of cathedrals, monasteries, and historic town centres, the lists of Spain, Italy and Germany clearly shows that it could have been worse. Interestingly, France has never made a substantial revision.

It may be of interest to compare the list of former TWHS with our Missing sites. I found seven matches:

2. Historic University Towns of Oxford and Cambridge - former TWHS Cambridge Colleges and Backs (UK)

8. Cultural Landscape of Santorini - former TWHS Akrotiri in Santorini (Greece)

22. Death Valley National Park (USA )

55. Chicago School of Architecture (USA) - former WHS: Auditorium Building, Leiter II Building, Marquette Building, Reliance Building, Rookery Building, South Dearborn Street – Printing House Row North Historic District (all Chicago), Prudential (Guaranty) Building (Buffalo), Wainwright Building (St. Louis)

64. Kaieteur National Park, Iwokrama Forest and the Kanuku Mountains - former TWHS Kaieteur National Park (Guyana)

100. Infrastructure of the Industrial Revolution in Britain - former TWHS The Great Western Railway: Paddington- Bristol (selected parts) is part of this proposal (UK)

119. Peaks of Sindou - former TWHS Falaises de Banfora associées aux pics de Sindou (Burkina Faso)

We have just found out that it did, although earlier than Italy and Spain.

I thought it might be interesting to go through the former T-sites and see some reasons for their exclusion and whether or not they should be brought back to the T list, as sometimes occurs (see recent Madrid and Azahara entries). I shall try to do that alphabetically.

Afghanistan:
Ai Khanum - A major Hellenistic city. This is the only major Greek site of this part of the Hellenistic Empire called Greco-Bactrian with some major findings. The site was deferred in 1983 due to conservation issues. I believe this is of OUV and could make to the list.

Algeria:
Sidi Bou Mediene - This site appears as a historic city, but in fact it is a mosque in Tlecmen, so included in the other former T-site. Deferred in 1982 for better management.
Atlas - Current T-list Parc des Aure lies in the Atlas.
Tlecmen - A major historic city with mediaeval mosques. Many parallels in Morocco, but none in Algeria.
Setif - A major historic city with Roman remains. Roman remains are already well represented in Algeria. Deferred in 1980 and again in 1981.

Argentina:
Cerro Colorado - A rock art site. Of less significance than Cueva de las Manos. Deferred 1987.
La Plata - City planning of the 19th century. Not of OUV according to ICOMOS. Withdrawn 2007.
Buenos Aires - 19th century architecture. Not of OUV according to ICOMOS. Withdrawn 2008.
Las Parinas - Proposed as mixed site. Cultural features are similar to Humahuaca (WHS) and Clachaqui (TWHS). Geological features of great importance according to a thematic study. Cultural features not unique enough. Would certainly have a chance as a natural site.
Cabo Dos Bahias - A major natural reserve in Patagonia unique in its marine wildlife. Similar to and less significant than Peninsula Valdes.

If I remember correctly, ICOMOS rejected it because it didn't believe that the concept of "urban cultural landscape" made sense in the way that Argentina presented it. Some elements of Buenos Aires's architecture could still have OUV.

I have just read ICOMOS evaluation of Buenos Aires from 2008:
http://whc.unesco.org/archive/2008/whc08-32com-inf8B1e.pdf
PDF page 352

The evaluation criticises Buenos Aires for not demonstrating OUV as a whole. Its architecture, urban fabric, city planning, historical development, interaction with the river (Plate) and the attached technical amenities are all described as not significantly different from many other cities in Latin America. Montevideo across the River Plate is repeatedly mentioned as an example of a very similar city. Although the evaluation directly tackles the concept of CL for Buenos Aires it does not suggest any alternatives. Practically it leaves Argentina no alternative to renominate Buenos Aires under a different criterion.

Bangladesh:
Sitakot Vihara - A Buddhist monastery from the 7th-8th century. Very similar to Paharpur (WHS) as well as Halud, Jaggadala and Mainamati (TWHS), all of which are of about the same age and style.
Diangar Pahar - If I recognised the site correctly it is a central square in Chittagong:
https://en.wikipedia.org/wiki/Cheragee_Pahar_Circle
I could not find any information about it, but it does not seem to be too special either.

Belarus:
Minsk - A representative example of postwar Communist architecture. Still missing on the list and of OUV.
Brest - As already discussed in the review the significance of the site lies in its role in WWII. It is of great importance in Russian (and Belarusian) nationalism. It is questionable, however, whether it could pursue a line of OUV.
Kamyanets - A mediaeval frontier fort. Difficult to imagine OUV.
Gomel - A Neoclassical palace. Similar to the palaces around St. Petersburg and of much less significance.
Mahilyou - A Russian Baroque monastery similar to Novodevichy (WHS), but of less significance. Probably difficult to demonstrate OUV.

Belgium:
Freyr - Yet another 17th century European palace. Its location at the Maas river is beautiful, but not different than many other European palaces.