Segwit2x aims to start sending signature data separately from the blockchain on 21/07/2017 and then to double the block size limit to 2MB in three months' time.

BIP 91 states that if 80% of the mining effort adopts the new blockchain software involved and uses it consistently between 21 July and 31 July, then the wider community should accept this as the solution.

the idea is that close to 90% of miners likes the idea, according to Coin Dance.