Many of the proposals for the fork include a voting mechanism for miners to signal that they are upgraded. However, miners very easily can lie about their intentions. A miner may wish to trick other miners into mining the fork, then continue to mine the small block sizes in an attempt to have less competition by having miners waste efforts on a fork that will be orphaned. Votes will be extremely hard to trust.
https://medium.com/@allenpiscitello/how-the-great-fork-will-occur-160f0e462371