Price upwards when it happens? I think it won't affect bitcoin price since most users won't feel difference after upgrade & most media won't share about that.
If Bitcoin forks (and especially with 75% vs 25% of the network) there is going to be a (negative) effect on the price. The network will essentially be damaged due to a split. Just imagine the great situation once media starts making articles with titles such as "Bitcoin split in two", "Confusion/panic in the Bitcoin community", etc.
BIP101 would have seen the block capacity grow into the GB range. The 2MB bump is an ultra-conservative needed fork.
Why? Because you say so?
Because of various assumptions based on propaganda, one of them being "Blockstream is evil". If Blockstream is evil, then Segwit must be evil too.