H.265 supposedly features much improved compression, so as long as the console supports that you could fit 4K feature movies on current BR. Or that's the impression I got from some article I read on the subject somewhere anyway.AFAIR these consoles are both supposed to support 4K video - which I guess requires that.
Then again, that piece might have been poisoned by biased PR fluff/spin, meaning 4K on 50GB BR would be akin to youtube 1080P streamed video, I'm not sure. Heh.