Once it becomes clear that BTU is going to happen (ie RV and others are forceful enough and larger miners are on board, heading for 51%), then the economic overwhelming majority would have no reason not to go with it.
I disagree. The economic majority has a multitude of reasons to not go with it.
That may well be so , and the fork will not happen. However IF the tide of opinion flows towards the fork, then the majority would have a strong monetary incentive not to dissent further. It may be best not to have the new code at all, but I point out that it is better to have BTU on one chain than keep both chains going : It is only the latter which will cause serious problems.
Possibly I am underestimating the propensity of people to cause themselves harm by non-cooperation. (ie prisoners dilemma etc)