At the moment 88% of the minters are signaling that they will implement segwit2x.
If this holds these miners will mine Segwit blocks before the end of July.
This basically means that the remaining 12% of miners could mine old legacy blocks but given their they are in the vast minority it is expected that they will follow and also mine segwit blocks.
Expected, but what if they don't??
This mean there would be 2 coins no?
Well it is their decision if they will not follow the majority of miners. If that happens, their mined block will be useless, I guess, since no other miners will accept that block in processing transactions. So basically, the "undecided" will be forced to go for segwit or they are doomed to fail as a miner.
If a split happens, there will be 2 coins (a duplicate of the original) and which ever chain is supported by many users will be deemed as the "original"