Is this question a bit misleading? First would not the soft fort in question would have to be first have to be created, then a proposal created, then the community and core devs approval to have the PR accepted? This could take years.
THEN, the soft fork software would be ready for the miner nodes to actually use to implement.
No; if 'the majority of hashrate' was in some way or shape a coherent entity, they could take 5 minutes to write whatever code and run it right then and there.
So, it would not be the a release from the Bitcoin core team, but a different brand of the Bitcoin Core software?
It in that case would not be a release from core, correct. It would not even have to be inside the client, they could run a seperate program to adds the additional softfork rule and enforces it by ignoring the now newly unvalid tx's...its janky, put possible.
