I disagree with a Forretress rise for reasons that were already highlighted in the post above me, but one thing that I think is important to understand is that referencing Weavile doesn't make for a good argument at all. We don't know whether or not Weavile will be UU, so using it to justify any arguments at the moment doesn't really produce good discussion, considering it could be re-banned in two weeks time.
Before I leave, I would like to discuss some nominations I have of my own that I feel would better reflect the current metagame. Here they are:
Suicune up to B+: This one has been discussed a lot lately, but I think that it's even more justified what with the new drops. Vincune was already an amazing set prior to dropping, with easy setup opportunities against top tier threats in Mega Aerodactyl, Scizor, Gliscor, Swampert, Krookodile, and more. However, with some our most recent drops, Suicune is finding even more opportunities thanks to its ability to comfortably tank hits from Pokemon like Mega Beedrill, Mega Swampert, Mamoswine, Mega Steelix, and Buzzwole, who have all been seen everywhere ever since their entries into the tier. Not only can it use a lot of these new Pokemon as setup targets, but it can also use them as teammates to help enhance its chances of sweeping late-game. For instance, Mega Beedrill and Mamoswine can adequately pressure Hydreigon and Latias, who can comfortably tank Scalds while wearing Suicune down. Mega Beedrill, Mamoswine, Buzzwole, and Alolan Muk can pressure the Grass-types that impede Suicune's sweep. Electric-types are dealt with by Mamoswine, Mega Steelix, and Mega Swampert (and to an extent AV Muk), and Water immune Pokemon can be stopped by one of Buzzwole's coverage options or by Xurkitree. Overall, Suicune's really benefitted from the drops in that it uses a lot of the more prevalent ones as Pokemon to tank hits from and set up on, while also utilizing them as partners to remove the only things that usually are capable of halting its sweep. Please rise this thing, it really deserves it!
Jellicent up to B/B+: This thing is so good right now. The new drops supplied it with a TON of threats that it can really adequately keep in check thanks to its great bulk and ability to burn physical attackers. Buzzwole, Mega Swampert, Mega Beedrill, Mamoswine, and Mega Steelix are all drops that it's capable of really easily keeping in check, which is really amazing considering these mons prevalence. It can also adequately check mons that remain top tier threats in this new meta, like Mega Aerodactyl, Scizor, Cobalion, Terrakion, and Infernape. The amount of threats that Jellicent can keep at bay alone is just absolutely amazing, and its ability to form really potent cores on balanced and defensive teams with great defensive Pokemon like Amoonguss and Hippowdon really allows for it to be easily fitted on teams. Overall, it's so much more consistent than everything else in B-, or at least has a much more appreciated niche, which overall is grounds for a rise to at least B in my opinion.
Toxicroak down to C+: This was brought up a few times already as well, but has seemed to get lost in discussion. Overall, Toxicroak really struggles in the current meta due to a plethora of reasons. It's main function is as a setup sweeper, but both its Swords Dance and Nasty Plot sets have competition from other Fighting-types. Terrakion and Cobalion generally outcompete it as Swords Dance users, as both can boost Speed, take on a larger number of threats, and have more setup opportunities due to either better bulk or the ability to force more threats out, while Infernape's generally better as a Nasty Plot user due to its better Speed (Salazzle also gives it some heavy comp as a Poison-type Nasty Plot user, due to its better Speed and typing for setup). While its Water-type immunity could be brought up as an argument, I feel that the fact that most premier Water-types beat it with Psychic coverage they often carry (Primarina, Starmie, Mega Shark) and that others have other moves to nail it with (Mega Pert with EQ, Volcanion with Fire Blast or Earth Power) sort of means that Toxicroak will only be able to put its ability to notable use against mono attackers like Suicune or Pokemon that don't threaten it with their additional STABs or coverage, like Tentacruel and Mega Blastoise.
Thanks for reading!