The "you have to use Daleks every year" thing was definitely a thing back in the RTD era stipulated by Nation's estate (never forget, the new series nearly never had Daleks at all as the Nation estate were enormously aggressive negotiating the rights) but we've never really heard from Moffat if it's still a thing. The series 6 cameo has always made me think that it's the case though.
Speaking of which, I've just found the article when negotiations broke down and it has possibly the best line I've ever read:
He said the BBC had tried to commission a cartoon series about gay Daleks for BBC Three.