Sultan, the Apache doesn't need justification. It's already there. Just to give you an idea on how multi purpose platforms arrive from specialized platforms, the Navy finally decided that the F-14 could indeed be a ground attack platform ... and sure enough, it became one. Apache will do what it needs to do, and as I've suggested in some other discussions on this topic, some of the "scout" function is already being done by various UAVs. The OH-58D is not leaving behind a vacuum of capability. The Army deploys with a mixed bag of tools.
The decision to retire OH-58D looks like a done deal. Whether or not that is a "bad" decision depends on subjective criteria. I don't see the Army reversing that, since decisions on force structure reduction in aviation must be viewed in context with all Army force structure reductions from top to bottom. Something had to go, so Aviation let go of OH-58D because the Other Programs were deemed to be a more pressing requirement to fund and support. I doubt anyone was happy with being forced to make that call.
On your last point: will X-2 demonstrated capability be able to scale up to the size and performance demands on S-97? It looks like Sikorsky is about to find out.