So like it seems, Bip91 will get through, but what will happen after?
I know its about bigger Blocksizes ect. but how long will it take after Bip91 gets confirmed until the new Blocksize will work for the Chain?
Bip 91 itself will not increase the block size or activate segwit. After it locks in, it will activate 336 blocks later. Then the miners will start orphaning blocks which don't signal for segwit activation which will cause segwit to activate 2 weeks after that. Thats it for BIP 91, though as part of the segwit2x plan, the miners will probably try to activate a hard fork in November to increase the block size. That part is very up in the air at this point at how thats going to play out.
Bip 91 itself looks very likely to lockin soon well before UASF.
The people signalling segwit2x already accepted that there will be a block size increase and at this point I don't think anyone is interested in destroying bitcoin so I think that will go off as planned without problems.
I think it's clear what they want to do. But I don't believe there is consensus on it with bitcoin users (unlike with segwit). So if Nodes, btc users, and exchanges refuse to follow the 2 MB hard fork, it won't really mean much since everyone will have to update to a new client to support it. They might or might not reach concensus by then since UASF for example already shows theres been alot of pushback against miner control.
If they agree, we'll probs just increase the block size.
If there is concensus not to fork, miners would either have to aquiesce or begin attacking the network (if they have a majority, they can make it so no transactions can be confirmed or they keep getting erased).
If users and miners are split, the blockchain would probably split for at least a while.