It is too early for coalescing, but that should take place.
After the results of the first debate or two might be a good time.
After the first couple of state primaries (excluding NH and IA), might be the best time.
Several southern states have moved their primaries up to March 1 or early March. That could have a signficant impact on the 2016 GOP race. If conservatives have coalesced behind one by that point, he/she could go a long way in gaining a big lead. If the conservatives stay splintered, they will hand the nomination to the GOP Elite selectee.
Cruz has coalesced himself right off my short list and he was at the top of it.