Bitcoin's future is decided via trading on open market, people who are confident in Bitcoin buy and hodl, people who doubt and prefer alternative implementations like SegWit2x or Bcash should sell their BTC and buy their altcoin. Alternatively, some people just hodl or sell both coins. This trading process decides what coin is the most profitable to mine at the moment, and the chain with most PoW is the most secure.
Making poll on a forum is useless, since it doesn't take into account amount of coins users hold. So, you could slightly improve it by requiring people to sign a message to vote. But still it won't mean much, because you'd need a few millions worth of coin-votes to make some prediction, which you won't realistically find here. Also, people can just lie about their intentions.
Agreements should be honored. One side got SegWit then other gets 2MB.
There was no agreement between "sides", all NYA signatories are just miners and companies from Barry Silbert group. No Bitcoin devs, no Bitcoin users.