I notice 5E is gunning for fast combat.
In itself though, this really isn't enough.
The issue really is the over arching design of play itself - if you have a session which is like starting at location A, then combat, then location B, then combat...combat becomes fairly pointless. You can only go from A to B then to C and so on. Generally GM's who use this sort of format start to choose really weak enemies, have the enemies use dumb tactics, and finally if the group is going to be killed, they simply fudge to preserve their A to B to C adventure notes. The party then fudge escapes, comes back and does the combat, so they can go onto B. Thus the combat is pointless - it's idle number crunching, since once of it's results (TPK) will be ignored, and apart from winning, the option of running away rarely works without fudging or simply generous readings of the rules/slip straight over to supposed drama based resolution (which is really just stating fiction that gets the PC's to escape that no one will balk at as too much of a dues ex).
Making fast combat just doesn't untie this knot in itself! It just reduces the time spent on rolling for a pointless activity. It's like saying to someone roll 15 or higher on a D20 - but if you roll lower, we'll just say you rolled higher. Why. Bother. Rolling? "But we've halved the time it takes to do it!"
The need a system where
A. Combat can be lost without a TPK happening and either without the GM having to fudge/simply narrate the escape, or just be upfront in the rules and say 'To stop a TPK, the GM can narrate most or all of the party escaping (preferably all)" and make it clear that fights really aren't to the death. You can roleplay the characters to think they are facing life and death, but as players lets stop pretending characters really can die. You think that, but when rather than one PC death looms and instead it's a TPK, the GM just folds and narrates your escape. So let's be honest about that. If one of you is likely to die, probably the whole party is about to TPK. Therefore the GM will narate an escape, therefore no ones going to die.
B. Give instructions for building stories where retreat actually makes a difference. Maybe because you were beaten back, the princess gets a curse put on her before you can rescue her. Heck, maybe she even just gets sacrificed? Make combat matter - be honest with yourself and don't really believe that you could die and that's what makes it matter. Your GM will fudge, so no, that doesn't matter.
Of course, in the end as you can tell from most WOTC modules, their own modules are A to B to C affairs.
So it's not going to change. It's going to shorten pointless combats and condition people to think it somehow matters to do these (since such a hullabaloo in the text is made about combat).