Sony would be better off backing away from this game and concentrating on other IPs

they are on contract, so hard to say.

This is true, but most of the exclusivity rights only last a year in most cases, so it is very possible for them to pull out for what will be year 2 of Destiny 2. On the other hand, continuing their console dominance over XB1 by continuing this deal no matter how trivial could still be a motivating factor for them, so its hard to tell. Reports are saying that the PS4 is in its final phase, so there is plenty of things that that money could be of better use for. This is just all speculation and wishful thinking on my end, anyways. I've fallen so out of love with Destiny that I'm not even sure I'll get the September DLC, even if it is the best thing to happen to it since release. Just have to wait and see and hope for the best.

I think their deal with Sony is actually release wide, the exclusives are released with a minimum year, but think the deal is longer.

Not saying you're wrong, but reports I've read only confirm exclusivity up to Fall 2018. With both Bungie and Sony being tight-lipped about their deal, I'm going to try and be optimistic.