I don't think so. You can't sue a company over something they don't do. If WhatsApp doesn't want to offer their app on WP, temporarily or indefinitely, for any reason, that is their choice to make.
Anyway, this is just speculation on my behalf, so no point arguing over it. I just seems strange to me, which is why I brought it up.
WhatsApp has always been a flaky app (likely because they are trying to shoehorn an Android app onto WP, instead of developing a WP app the way it should be developed). I can think of a few occasions where WhatsApp had more serious issues than what I'm witnessing now, yet they didn't remove WhatsApp from the store then. My personal experience is that WhatsApp actually works better today than it has in the past. In fact, during the time it's been unavailable in the store, I've been using it every day without issue. Under such circumstances, pulling it from the store seems extreme to me. Considering that the issue is specific to GDR3, which has been out for quite some time, the timing also seems strange. Why now, precisely at the worst possible moment, when the first WP8.1 handsets are being released? Why didn't they pull it from the store months ago when GDR3 was released instead?
Don't get me wrong. I'm not saying this is what is actually happening. It just wouldn't surprise me it if was.