Is there a time limit in Overwatch?

Solution 1:

From Overwatch latest PTR patch notes :

Competitive Play

• Fixed a bug that could cause overtime to continue indefinitely on Assault maps

So yes, if you are unable to recapture a point, after a certain amount of time, the game will instantaneously end, giving the win to the team that currently controls the point.

Solution 2:

During the open beta I was in a match on Ilios (well) that seemed to hit a time cap. Both teams had reached 99%, but due to each side having a teleporter, the overtime was endless. Eventually the game just suddenly ended and the team in control at that time (my team) won the round. Everyone in the comments was rather confused. I can't remember exactly how long the match was, but it was long enough for people to start noticing.