This has 3 answers:
1. On the popular labels of the time, yes, since Federer & Nadal still have tremendous presence and it's catchy.
2. On realist terms, Wawrinka has won more Slams since his first than everyone except Djokovic. But calling it Big 2 isn't gonna fly.
3. It's really a transitional era with Cilic winning one and Wawrinka taking hold with Murray in the fold, so yeah.