Well, first, can you guys try to keep your full answers in a single post? double/triple posts sequences are a bit strange... aye? Just edit your posts.
Well, concerning the classes for solo, every and all classes may be soloed on SoA, so I guess that if the game makers keep with D&D 2Ed (wich I doubt, they'll prolly use 3rd or another edition) the classes could be the same as in BG2, of course with more classes. The rogues, for example, are really deadly machines in SoA, depending on how you use them. With a bit of cheese they are just unstopable. And multiclassing a mage and a thief is sometimes better than multiclassing a fighter mage, if you are a good backstab user.
So, I think they could keep the same classes, but I agree with you guys regarding the need for a solo option for the game. To chose wether to be with a party or not is important, and really challenging for those who are already long-time players.