I have no doubt that somehow, some way, they’ll revive the speedforce. It’s the holy grail of speed as far as speedsters go, and without it, the likes of Wally, Thawne, even Zoom (he’s existed in this new post crisis timeline, right?) shouldn’t have their speed.
We know that Thawne created his own speed force, and yet the actual speed force still perused him when he altered the timeline too many times. How is that? It wouldn’t surprise me if, somehow the negative speed force coexists with the actual speedforce, and without one, the other cannot exist - at least for a prolonged period of time. Maybe Thawne is running on borrowed time too?; but because he (presumably) doesn’t use his speed as often as Barry, he’s not yet noticing the changes.