This is very true. Now it looks like we have to make out guesses on. It appears that half of Unova is completely covered in ice, as well as the town you start in Black and White. You are a completely different trainer in the previously inaccessible western part of the Unova region, set 2 years after the original. What's more, there are new gym leaders throughout Unova.
Unova in Black and White:
Unova 2 Years later in Black 2 and White 2
New Character to Choose From
New Rival
New Gym Leaders, Featuring Homika (Poison) and Shizui (Water)
Mysterious Akuroma
Pokemon Black 2 and Pokemon White 2 Official Japanese Trailer
Now for my new Hypothesis on the plot theory of Black 2 / White 2 (ASSUMING STORY REVAMP)
You are a new trainer (who in my opinion happens to look alot like the two trainers you start off with in Black and White but whatever) with a new childhood rival. Game Freak can never seem to have a pokemon game without a childhood rival for the most part. Implying this is two years after original Black and White, I assume they will keep the original trainer and N as the two Heroes for Zekrom and Reshiram, who should play a role in this plot line. Perhaps something like Red did for gold and silver. Ghetsis, I would hope, plays a role in this as well since he was never caught. All the Team gangs in previous Pokemon games have all finished and split up one way or another. Ghetsis was behind the making of Team Plasma to use N as a means to accomplish his evil plans, till they backfired of course. Now he is MIA, waiting to be caught.
Now for Kyurem. Obviously you were able to catch it in Black and White, but seeing as how it is the main legendary Pokemon in this game, I assume they are revamping it to where it was never caught, but rather waited for some unknown reason to emerge, which leads me to my next theory: the ice-covered Unova. It appears that Unova has hit its own ice age. This may very well be due to the roaming of Kyurem, possibly in its new form. It has the most powerful ice move in its arsenal. This move, Freeze Burn/Freeze Bolt, may be its move that it used to do this on Unova. Perhaps it may have been Glaciate, as we saw how well it covered the crater in Black and White in snow.
New Gym Leaders are here. In black and white, the gym leaders formed an alliance and helped defeat Team Plasma. Either they left for some reason regarding Team Plasma, be it searching for Ghetsis or whatever, or left for another reason. THEN AGAIN, we may only have a few of the gym leaders replaced, not all. Basically though, I haven't got the slightest clue why they would change gym leaders.
Last but not least, the mysterious Akuroma. He is very mysterious, seeing as how hardly any information, if any, was given about him. My guess is that he is a new leader of Team Plasma or a new Team. He should be playing a role similar to that of N.
Anyways, that is my two cents on the matter. You can point out your theories as was the point of this thread and NOT criticize, at least without good evidence to back you up. Also, any and all theories may be tossed out the window regardless what any of us guess. It wouldn't be the first time Game Freak (or as I refer to them as like many others, Troll Freak) trolled us....