With the integration of the old CO fleet, is it possible UA may become more conservative and start blocking some E+ seats on legacy UA planes, since an equipment change from UA to CO plane would dump a lot of folk into the cheap seats?

It's going to take a while before the combined fleet has adequate E+ availability (if it ever will). The new UA now has twice the demand for E+ but only fractionally more E+ (or equivalent) seats available than before the merger. If I were UA, I'd be looking to lower expectations quickly!