I think personally the land would have suffered greatly, as seen before when they where killing halfbloods a mountain of preys bones. Having all of Riverclan would be too much for the territory the lives in and would be forced to relocate from the original clans territory with so much mass.
I feel as though as the clan grew more cats would be scared to fight it so they would convert, hence making it larger and depleting numbers of resistance to the point where no good cats could do anything... so they would revert to being rouges and loners so Tigerclan would control most of the forest. The loner population would decrease by lots and I feel as though somehow bloodclan would be drawn into the mess somehow.