is Clip going to be part of edge replacing integrant ?

IIRC I've asked this before and the answer was yes, when Clip matures enough.

Not replacing, as well as

There's a branch with clip support, use at your own risk

Is it just for the sake of backward compatibility? Or does the combination of Clip and Integrant somehow give some benefits?

I use Clip in a production app

It works really well

Backwards compatibility. They probably won't be usable together, just checking for one key or the other.