This might be a dumb question, but: have we ever had a contentious hard fork before? What will plenty of notice look like?
Good question. I believe the plan for classic is to go straight to 2mb
but I'm sure there will be a notice period and there may be a trigger. They plan to release end-of January so that's fairly short. BIP101 had a trigger and then a wait to give the network chance to catch up. Unlimited is a bit of a wildcard as it's designed to follow the network.