The two engine long haul ops will continue to replace 4-engine types on many routes. This is clearly evident from developments so far.
4 engines, for all but a very few ops...are dead as a doornail.
Except...possibly freight, and even then, as two engine freighters become cost effective in the future, freighters will become twins.
Just the way it is...like it or not.
The only exception is the MD11, but not all that many of those are available.