Segwit2x developers plan to allow bitcoin miners to run the new software at block 494,784 on the blockchain which they predict will occur sometime in November 2017.

Also not quite accurate. Miners were invited to run the btc1 software (the official SegWit2X reference implementation) already in July (or was it June?) - but the btc1 and Bitcoin Core will become incompatible sometime in November, possibly creating a chain split.

I have tried to describe some scenarioes in Bitcoin Forks for Dummies. I'm a bit optimistic, seeing that the Bitcoin Cash-esque "free money" may be the most likely outcome - but we'll see lots of FUD and propaganda wars before November.