7.3 Patch Speculation
Reading the patch 7.3 notes will give you a pretty good idea about who's been popular in professional play. Just about every pick-or-ban champion - with a couple exceptions - received nerfs of some sort, which puts a lot of the professional meta into doubt. While it's anyone's guess as to what will still see play, we can at least make a few guesses based on the changes.
The Big 3
All of the members of the "100% Pick or Ban" club got nerfed in some way in 7.3, but it's Camille who received the biggest changes. Her damage and stickiness were dropped across the board, with hits to Precision Protocol's damage, Tactical Sweep's slow, and Hookshot's bonus attack speed. It seems like a lot on paper, but Camille's biggest assets - long-distance initiation, Hextech Ultimatum's lockdown, and her incredible damage - weren't really touched. Camille may get through the ban phase in 7.3, but I fully expect her to remain a hotly contested pick.
Rengar and LeBlanc have a smaller changelist than Camille, but are still getting toned down. Rengar's losing his empowered W's CC immunity and a bit of his ultimate's duration, while LeBlanc's passive damage has been nerfed. I don't expect the LeBlanc changes to do much to her banrate - it's a pretty small nerf to her kit - but Rengar may very well get through more often now. He was already the least-prioritized of the three, and having a weaker assassination pattern might be what kicks him off the pick-or-ban list.
Taking down junglers
Kha'Zix has been first picked in basically every game he's not banned, which should tell you something about how strong he is. Basically no one can fight the Voidreaver in early jungle skirmishes, and his Evolved Claws allow him to solo drakes with ease or chunk down tanks. The nerfs to Taste Their Fear will help make Kha less about sustained damage and more about bursting champions, but I ultimately don't think it'll be enough to knock him down a peg in the jungler standings. A 45% CD refund on evolved Q just means that Kha will take longer to kill tanks or drakes, while doing nothing to address his burst pattern against squishies.
Ivern, on the other hand, may suffer a bit more. Daisy's defenses were hit pretty substantially, and since she no longer regenerates health out of combat it means that his ultimate can be shut down far more easily than it was before. With Daisy dying sooner, Ivern doesn't offer much else in fights, as his frailty means that he's easy prey for someone like Kha'Zix. Ivern's unique jungle shenanigans may keep him viable in the professional meta, but I expect to see him supplanted by the likes of Rek'Sai and Lee Sin in the coming patch.
Reducing support and bringing down the hammer
The most contested supports in the current meta are also taking hits. Zyra's plants no longer automatically attack nearby champions - unless they were hit with the same spell that spawned the plants - and Malzahar's voidlings are easier to kite. Both are fairly light changes that probably won't affect their contested status, but it does help open up the support pool a little more. Melee supports like Braum and Taric will probably see more use, and it's possible that Nami might rise to become a staple pick for teams who don't value Zyra as much.
Finally, Jayce was targeted by a few nerfs, mostly aimed at his hammer stance abilities. With reduced all-in potential, Jayce may potentially drop from being a must-pick champion into simply another strong toplaner. If so, it's more than likely that the toplane tanks we've been seeing - Maokai, Nautilus and Shen - will be a lot more heavily targeted by bans, with teams using Kennen or Poppy in the event that Jayce does get locked in.
Ultimately, Patch 7.3 isn't likely to bring out many off-meta picks or reestablish old trends. However, it does have the potential to shift up which champions teams are willing to ban, bringing us to a more fluid champion select.