do you think they'll finally take the opportunity to upgrade the type chart in B2W2? I'm aware they haven't touched the types since generation 2 (and that was likely only because of Steel and Dark being introduced, as well as fixing glitches from gen1 such as Ghosts having no effect on Psychics), but there are a number of factors to consider. First of all, this is a new paired version within the same generation. It isn't a third version, so if they wanted, they could make trade/battle compatibility be designed to mostly work between these two versions, whilst compatibility with the older games is more secondary (kinda like how Pokemon fitting specific requirements could be used in Gold/Silver/Crystal's Time Capsule, or they could have the game's battle system adjusted whenever battles with older games takes place), and should they go that route, they could use new type compatibilities without much complication. Several attacks could be overhauled as well (for that matter, how does Hypnosis work when linked between Diamond/Pearl and Platinum/Heart/Soul?).
There's also the matter of the games' mascot being an Ice-type, which GameFreak seemingly has yet to notice is HORRIBLY flawed in terms of defense. Seriously, a resistance to Flying, Bug, and/or Water would make sense (some Flying and Bug attacks are wind-themed), and probably wouldn't break the game... hell, if the overly abundant-yet-lacking-weaknesses Water is resisted, that could only help. Offensive Flying and Bug, meanwhile, don't seem to leave a huge impact (but could still give Ice something in terms of a resistance), not that Ice is an abundant enough type that those types would in turn be further screwed over anyway (hell, if Ice suddenly gained a Flying resistance, the only Pokemon that would become 4x resistant would be Frost Rotom).
yeah, that's probably true. However, it is worth noting that this is the only true sequel we've had ever since Gold/Silver. I'm aware this isn't gonna be a new generation, but even without the addition of new Pokemon (forms aside), the mechanics alone were changed considerably in Gold/Silver, all while still being compatible with the predecessors.