Microsoft and Sony both said that this generation of consoles will last about 10 years. So it's most likely that TES V will be for this generation of consoles.
Just because they said they are going to
last ten years doesn't mean they are going to be the latest generation for ten years. The Playstation 2 lasted for far over its lifespan because of Sony and developers' support but it was not the latest Sony console.
What I expect is that they plan to release new consoles rather soon but still support their old ones rather heavily so that they can make the most money out of them as they can. This is because both the Xbox 360 and Playstation 3 were rather large money sinks to the companies at the beginning of their lives, whereas the Wii was a huge success and made far more money than Nintendo put into it. The 260 and PS3 are still struggling to make a profit, especially in the face of setbacks like the red ring or the PS3's high price tag that plagued them for so long.
I am not sure if we will see TESV on this generation or the next. Both the 360 and PS3 have a lot to offer still, both graphically and hardware. What some people fail to understand is that, despite having worse hardware than a computer, a console has much less work to do because it has no (or few, as most of today's consoles have a sort of desktop running in the background) programs running in the background. They can devote the majority of their power to running the games they play. Proper optimization can make use of this and make a 3+ year old console run a brand new game as if the console had never aged. Hell, just look at Halo 2 on the Xbox. It pushed it to it's limit (so much so that the cutscenes had to load in 4 parts and you could see that loading at the beginning of the scene) and the game looked beautiful on a console where Halo:Combat Evolved once looked great.
I don't believe that there should be any limitation to having another TES game on modern consoles, but Bethesda may also be negotiating with Microsoft or Sony such that their game would be a release title on their newest systems, as with Oblivion (well, almost if it weren't for the delays).