i really don't think the tiers are going to change much outside of adding the 5th gen pokes
there isn't a significant change in the metagame this gen, unlike the past few
yea there are new items, moves, abilities, etc, there just isn't a complete overhaul of the system like there was in the past 3 generations
basically what was OU 4th gen will be OU 5th gen along with the OU 5th gen pokes, and you can go down the list
the pokes i feel that will most likely move out of OU are infernape and snorlax
they got hit hard with all the new additions, it's much harder for them to pose threats for teams, heck snorlax was barely a threat in gen 4 and it has a harder time in gen 5 from the looks of things
with SS teams running around, dory and garchomp are going to be everywhere, infernape cannot outrun dory in SS (no matter what) and it can't beat garchomp straight up without HP ice (in which is a 2HKO no matter what while nape gets OHKO'd)
this is also assuming no Dream World abilities, with them, there's a huge mix-up as Ditto becomes the only revenge killer you'll ever need, garchomp and dory are nowhere close to being broken, shandera is a monster, and there are a whole bunch of new toys for the old guys to take care of
but in general, gen 5 seems like it's going to be gen 4 with more pokes
the only gen 5 items i see are balloon and evolution stone
one thing that might change is the machamp leads, i don't see them anywhere