I don't see how Magic Guard will do much for Celebi, as it already has natural cure and is immune to spore, sleep powder, and leech seed. Sure it is a slightly better ability as it doesn't take any damage from status while its still in, and it doesn't take stealth rock damage, but I don't see Celebi's role changing much. Maybe I'm missing something important, but I don't see much of a rise in viability, as its biggest problems, Talonflame, Aegislash, anything with u-turn, and Bisharp, still plague it.