I don't know, UU had Moltres (alebit barely because it came close to being booted), Yanmega, Milotic, Venasaur, Blaziken before speedboost, Registeel, etc last time. There is absolutely nothing wrong with Swampert but I don't see he'll remain OU tier (not that you couldn't use him obviously). He's not a Gallade/Heracross/Honchkrow tearing apart UU/BL (assumably, although it could happen, just not likely). Actually, it had Torterra who is somewhat similar to Swampert in that it countered physical Tyranitar (although Icebeam will kill Torterra) with high defense and hp and setting up rocks. It has Swords Dance/Rock Polish/Growth/Stock Pile to boost it's stats (not all on the same set obviously). It has Leech Seed to steal hp and also gets a stab on Earthquake, had the key rock resist, etc. If anything, I predict Torterra would sooner move up in OU (I don't see why not, it's great and Ice is less common than Dragon moves now, sets up Stealth Rock, better bulk than Swampert, can smash through unfortunate waters (watch out for Icebeam but you could use that to get something else in since it is such an Ice lure), especially that stupid face Quagsire, immune to Sand...)I still wouldn't use boiling water with it though. and even though it didn't really get anything. I think it will stick around for a while. it would be too good in the lower tiers imo.
Before I turn this into the virtues of Torterra, I do believe however Swampert just isn't going to be as good around this time as he was last. Bulky waters need to have a non-Rest sort of Recovery and it's outclassed by that (and generally bulkiness) by Vaporeon, Slowbro, Quagsire, Gastrodon (lol how the tides turned), etc. Slowbro especially excites me because of Regeneration and the Fighting resist, something important to have. Swampert will have a nice comfortable home in UU where Milotic and the rest of the good but not good enough but used to be pokes have all gone out to pasture. He'd be very good there (in competition with Blastoise, Samurott, Milotic, and Feraligator although I do believe Feraligator might actually jump to at least BL OU because of Encourage and I just can't believe it would stay there).
What would be to good for the UU is Latias (usage wise). I mean seriously?