Their (new) client's implementation could very well independently violate another patent or an unknown extension of the licensed patent. What would they gain from taking on this risk?

The broken patent system has bumbled along precisely because large companies generally have cross licensing deals with each other, leaving only the little guy subject to vague infringement claims. Now that there's a well-funded company which doesn't require 'incoming' licenses (by not making anything), there's real money involved for the big guys.

On another day I might be arguing for abolishing patents, but I just don't see how this is an abuse of the current system.