PoE is real-time. Turn-based may have it a bit easier (but not "easy" in itself.)
You need networking code that connects players, make it secure, introduce a matchmaking server and maintain it, you need to relay information on actions and possibly "predict" actions and movement, synchronise all that stuff, make sure it always applies the same results at all times on several connected computers at once, doesn't lag even with wildly different hardware, and so on. And you need people who have experience doing that stuff.
You don't just tack that on cheaply in a patch.
If they had the resources, sure - but I really doubt they have.
Now, I really enjoyed using BG2 and IWD as a kind of interactive chat program with gameplay elements back in the day. But really, with "coop modes" like those in a modern game, you'll get slammed in the ground leaving a crater.
Edited by Varana, 21 March 2017 - 06:11 AM.