The comparison between UU and OU was just that: a comparison. We aren't saying that more UUs will suddenly become viable. We are saying the metagame will become more diverse (with other OUs becoming more used).
As has been mentioned multiple times Salamence is in a tier all its own when it comes to offensive prowess. Everything else in Standard has situational counters, and some things have hard counters:Tyranitar will find it difficult to ever get past Machamp without using Zen Headbutt or something. Mix Mence doesn't even have situational counters. The standard Mix Mence set has 0 things that can come in on it safely more than once (Cresselia comes close but the popular sandstorm keeps it from being able to recover effectively.) It isn't like a lot of other pokemon where you might lose something to find out what set it has and then you know what to bring in. With Mence you are never safe. It can do 60% + to almost any switchin and has plenty of opportunities to come in and roost off damage and start the Grinding again. It is even able to counter things for you (namely Lucario and Breloom), unlike nearly every other top tier sweeper like Lucario, Infernape, and Gengar, which can't counter anything really because of their incredible frailty . It is very difficult for me to believe any argument based on the idea that there are other pokemon that are just as good as Mence that should also be banned. That argument, when folllowed to the logical end point, is essentially the same as the "slippery slope" argument, which is a known logical fallacy. If you wish to argue please do so in a logical manner.
Saying that Mence shouldn't be Uber because it isn't as good as other Ubers is ridiculous. It doesn't matter how good the other Ubers are. If Mence is too good for the rest of OU then it should be banned. And it WOULD have a niche in the Uber metagame anyway. It has more speed than Rayquaza (which lets it tie Palkia), and it has the useful intimidate. It also has roost, a move that Ray really wishes it has. It is already being used as a Rayquaza partner on a lot of teams.
Dragonite is in no way comparable to Mence. Intimidate, 1 Atk, 10 SpA, and 20 Speed is HUGE. It makes Mence physically bulkier upon switchin, and allows it to hit harder and faster. Dragonite is too slow to outspeed Lucario or base 100 scarfers at +1, 2 things that Mence really enjoys to do.
The reason stall is so common is because stall is always common in a new, limiting metagame. Once the new metagame becomes more established there might be less stall. Perhaps instead of whining about how terrible stall is you should build a team with some synergy instead of relying on Mence Dragon spamming to break through stall teams. If everyone built competent offense then stall would cease to exist.
Your logic regarding Lucario trends doesn't make sense. Salamence is THE premier Lucario counter for offense, and with it gone it becomes much easier for Lucario to sweep those teams. The increase in stall teams may mean an increase in Gliscor, which is problematic, but nothing a little bit of team building doesn't solve. Also, Lucario doesn't even counter Tyranitar. Any secondary attack from almost any set is a ko. The most popular set is DD, which outspeeds and kos with Fire Punch or Earthquake. A banded set has access to Aqua Tail and EQ. The scarf set kos with Superpower or Earthquake. Tyranitar IS good, but there are multiple good counters for it, Hippowdon and Machamp being the most obvious.
Regarding waiting for Black and White, we STILL need to establish tiers for Gen 4 just as we have done for every other generation. This doesn't change when a new game rolls around.