Overview
A huge patch is dropping to address some of the early concerns around the set (fights are too long and balancing is off). You can read the full notes here.
Ao Shin's Ascent goes live this patch. You can read about it in depth here, but this is the TLDR:
PvE mode
It's a sort of rogue-like game mode that combines many of elements of TFT with a PvE progression loop that can be unique on every playthrough
You can select augments and modifiers for bosses to tailor your runs
Gain rewards for playing
Live for just this Patch (15.5) and the next (15.6)
It's a rather in-depth game mode, so make sure to give their official article a read if you want to learn more, otherwise just play it!
As always, be sure to check out our comps page to get access to the best comps to play and the data to support it here.

Systems
Lots of Power Up changes aimed at removing bad options and allowing you to more easily hit something satisfying
Buffs
Traits
Crystal Gambit (3) buffed to better reward lose streaks
Monster Trainer Level Up system removed
Kog'Maw, Lulu, and Rammus just start with their abilities now
Units
1-Cost
Kennen heal buffed but damage decreased, which is fine since he's a tank...
2-Cost
Gangplank AS increased
Katarina damage increased
3-Cost
Kog'Maw, Rammus, and Smolder all significantly reworked numbers-wise to adjust for the Monster Trainer change
Hard to say right now if it's a net nerf or buff, but these units will be more flexible and should be something you can pivot into at any point in the game.
Neeko damage reduction increased
Swain's subsequent heal increased but initial heal decreased
Ziggs AS increased
4-Cost
Akali damage increased across board
Ashe damage increased across the board
However the number of arrows no longer scales with AS, so it might be a nerf overall
Volibear spell attack speed increased
Yuumi initial damage output increased but scaling damage decreased
Might still be bad
5-Cost
Braum AoE damage increased
Seraphine Friendship resist and health bonus increased
Nerfs
Traits
Crew Rocket damage decreased
Crystal Gambit (7) nerfed
Units
3-Cost
Viego AS decreased
Conclusion
Meta won't shift too much and it will take a bit of time to determine how the new Monster Trainer changes shake things up
Keep an eye out for Katarina and Akali -- some nice buffs may bring them back into the meta