The realistic thing here is that it is more likely than not going to be Skyrim, the important thing though is that there is precedence and precedence within Bethesda especially of an announcement and then an application for a mark. My initial post stated that it MAY not be in Skyrim... it is just that the mark is no longer an indicator of anything relevant in my book besides a possible game title. The wifi mark was certainly close to the original Skyrim game mark...
I get a very strong impression it's Skyrim. In fact, my impression is so strong I'd be surprised for Skyrim not to be the next TES V. The Skyrim trademark is there for a reason, if it's not for TES V, for which game/anything else would it be for? For a trademark to be dated since 2006, it better be important, and what is most important to the TES franchise than a major instalment? I'd be surprised if it was for a spin-off. Plus the first TES book following the events of Oblivion talk about the destruction of Morrowind and an Argonian invasion. Since Skyrim shares a border with Morrowind and the Dunmer folks are probably already used to deal with Nords because of Solstheim, I'd say it's logic for Dunmers to either try to seek shelter in Cyrodiil or Skyrim, they have no choice and Skyrim is a strong possibility. Since to me it would be logic for the books to foreshadow the events of TES V and the Morrowind disaster it would make sense, and with the Nords dealing with Dunmer and all that politic thing around it, I'd say it would build a very strong premise to a new TES entry.
As for the announcement, as much as I'd like it to be announced during the VGAs I'd be surprised. We all know Bioware has something up its sleeve, and it may not be the best idea to announce it at the same time as another rpg from such a renown developer who are still working on a very well selling franchise. It may not hinder much, but has far as pure hype? It would be diluted a bit, if people digest the Bioware announcement and then a month later Bethesda announces TES V, it would have a much bigger impact. While Bethesda would announce the sequel of an highly acclaimed game 5 years after the last, Bioware would probably be announcing the last chapter of also a very acclaimed trilogy.