sure it's likely that the 25% that don't agree with will fall into line, but can we really call 75% a successful agreement
lets all vote 90%
But that assumes all miners are paying attention. Which technically they are, but that's a factor of centralization of mining.
In an ideal - cpu mining from the client - world....75% would be more than sufficient.
let's assume that only miners that vote count, miners that don't make an effort to vote are said to throw away their vote and are not considered.