That's a tough question, it sort of depends on if you "need" it (do you have something that works, or are you needing something now), budget, how long you feel you need to keep it for it to be worthwhile, etc.
The 50V is a great piece, I love mine. 4K? It's not really baked yet, we still don't really know what the requirements for "permanent" 4K systems will be (gamut, HDR, bit depth, etc), and we likely won't until the 4K Blu-ray specs are announced which seems somewhat unlikely to happen soon, maybe holiday 2015 if we're lucky. Atmos, etc? What's that going to come on, Blu-ray? How many movies use it, and are you actually going to have the 11 speakers to get the most out of it?
Personally, Anthem's got a pretty good track record of providing some sort of upgrade path (you may have to act somewhat quickly), so if you're OK upgrading in a couple years, then a 50V now could be a good option.