It would be ideal to begin Gen 5 without any bans save for the ones on the titular cartridge legendaries. Anyone who wants to argue that keeping Mewtwo and Rayquaza banned is a bad idea can do so either now or then, but "good luck". One of the few precedents we've set that has made sense in hindsight is to ban the 680 BST legendaries. Again, and as I've suggested in a previous thread here, anyone who wants to argue to the contrary has virtually all the evidence in the world to make the case right now, today, that pokes like Mewtwo and Rayquaza were not indeed fairly tiered in Gen 4 from the beginning. I see no reason to entertain the idea of beginning Gen 5 with absolutely no pokémon bans until someone can make that argument.
Anyway, Stage 3 isn't quite done, but I am of the opinion that Manaphy's impending Stage 3-3 vote will have a ton of implication on how right everyone thinks they were about their predictions on our final tiers. Tangerine, for example, is convinced it will be voted uber by a supermajority. If this is true, then its failure to receive any kind of majority for uber in either Stage 3-1 or 3-2 would be rather "puzzling", to say the least. (It's 13-10 uber vote in Stage 1 isn't exactly a good sample size.) People have argued that it's because "everyone was focused on Garchomp" (81.5% of teams) and therefore Manaphy was largely ignored as an offensive threat itself. If this is true, then there is no logical reason to believe that future Suspects won't similarly be "ignored" in favor of the more popular Flavors of the Month. This is an problem with the "let's test everything at once" model, since it suggests that the more suspects tested at once, the more likely something will be overlooked since it was being "tested" in a less-true metagame.
And if Manaphy is ultimately voted OU, then one could wonder how wrong we were to assume it was so broken to ban it in the beginning of DP, or ban it after a very small amount of testing. Then you could argue that yes, of course we need to start Gen 5 with every non-titular legendary unbanned (as we will unless someone has a good reason), but this also underlines how crucial it is to NOT start Gen 5 with pokemon that a large consensus of us feel are uber, since it will likely hamper the potential of a Gen 5 Manaphy (or the Gen 4 one for that matter) until enough "Suspects" have been rightly banned.
All that said, I'm aware that this process is almost two years old now and has gone on for a very long time. Many of the processes will be streamlined by Generation 5, though, and I feel that the Suspect Test in Gen 5 will be able to begin with Latios, Garchomp, Skymin, Manaphy, and the ~1-2 legit Gen 5 Suspects we're bound to have. This is assuming Latias will no longer be a Suspect in Gen 5 (what a stretch), but take note that this also gives the same treatment to such almost-Suspects as Salamence and Scizor. I think a Gen 5 Suspect Test could be wrapped up in about six months once we agree on what pokes deserve to be considered Suspects.