I think for the most part, push-ups can replace most chest work quite nicely (with the benefit of working much more than the chest). But I personally will not swear off incline dumbbell work. It's what helps me keep some fake 'cleavage,' and when I don't do it for a while (even when doing push-ups and other chest work) I see the difference (even though some say that you can't isolate the different parts of the chest and they all work together).
You can, however, do a type of 'flye' when doing push-ups. Get some gliding discs (or a plate on carpet, or a microfiber cleanin cloth on wood) and use one under one or both hands, sliding the hand(s) out as you go down and in as you go up. YOWZA!