MegaGarchomp doesn't need an item, neither does MegaMewtwo or MegaBlaziken. They're still powerful even without the ability to use items. Mega Pokemon will be used more than everyone seems to think, because people always find reliable strategies for new things. If I can only use one Mega Pokemon, then I'll just put Mega Garchomp on a sand team, or put Mega Blaziken on a weatherless hyper offense team. And like Silver said, they're likely to just be alternate forms like Rotom-W, etc. Giratina-O being the best example because it holds the respective orb when you choose it. Mega Charizard will also be a good Pokemon in the lower tiers. Yes, I firmly believe that thing isn't going to be OU. I'm being generous even stating that I think it will make UU. Anyway, with a proper(at least better than Vulpix) sun set up Pokemon, it's a good reason for Mega Charizard to stay in lower tiers. Regardless, Mega Pokemon will be used. It just all depends on strategy, and how well you play. If I can sweep teams with a curse/payback Umbreon in OU, then I'm pretty sure buffed up versions of already powerful Pokemon will be viable. Item or not.