Isn't this why the "Limbo" tier exists on the main site?
Limbo is tier for mons whose tiering is yet to be determined. Now that D/P has been out for ages it is *suprisingly* empty, but when B/W comes out a lot of things will end up there... but hopefully not for long.
@ NU-testing: Neverneverused? Things like this shouldn't be abanoned just because a neat name doesn't immedeatly pop up. :P
If there's just enough people to make the ball roll it should be worth it:
NU deserves some more love... and little less MaggyTyphoZard overload.
And about banning things...
While banning mons might create more and more broken and even more broken threaths (imagine if Blissey would really end up in Ubers) metagame of no change can easily lock up.
Counterargument can be made about Ubers constantly changing while the allowed mons have been the same since Darkrai/Skymin arrived.
Correct me if I am wrong, but it still seems, that not a lot of "new stuff" comes up in Ubers - the changing is mostly in usage (IE now CM/SpecsOgres are more reduant than ScarfOgres). Quickstall Mewtwo maybe? Even the tier including the little floating pink DIY master Mew sees quite few of new startegies - and new pairings are hard to come by with 24 Ubers and select few standard mons - since not much is actually viable there.
But back to UU: the point is, that change creates change in playing. Who is more skille competitive player, the new one storming ladder now, or equally faring older player who knows how to handle Crobat with Registeel & buddies? Also, experiencing the change drives forward the same cause CAP does: finding out how metagame works.
While completely balanced metagame is enjoyable - and within some limits promotes new sets and strategies - it doesn't comapre to what a different metagame (of course on top of it!) can afford. Think about it, you more experienced battlers, can you say you did't learn something from roasting Shaymins with Moltres' Fire Blast, throwing Azumarril on the way of Honchcrow's Heat Wave - and of course making Crobat cry in pain before Registeel's Zap Cannon?