I'm "Aes".
I've been laddering pretty extensively to get a feel of the metagame, and my thoughts have been shaped a little by what I've seen.
Going into the test, I already knew stall would be affected much more than offense, so I tried to see the extent to which stall was made unviable, and how it could potentially adapt, as my first order of business.
Ubers stall flourishes in compressing as many roles and checks into six pokemon as possible, often finding room to add secondary checks to common threats or utility pokemon as well. This means using pokemon like specially defensive giratina-a, a great kyogre check as well as durable spin blocker and utility counter to many things, and is one of sun's two useful kyogre checks, as grass arceus loses a lot of its utility if its fire weakness isn't nullified, as it no longer walls threats like palkia and dialga.
But, even completely ignoring excadrill and the impossibilty of reliably stopping its spin while using stall, bar otherwise terrible sets like balloon gira-a, OHKO makes this extremely difficult. Kyogre in particular loses many of its few checks with the addition of a OHKO move. SpD giratina will now lose more often than it even gets to phaze kyogre out. Latias HAS to run Grass Knot or thunder to have a decent chance of checking Kyogre now, and now has even more of a limited choice of a coverage move if it desires to check both CM and OHKO variants of kyogre. Grass Arceus doesn't have to run anything unusual, but obviously still has the same 51% chance of being ko'd.
At first I attempted to use a somewhat standard stall team, and as expected Gira-a can no longer check kyogre reliably at all, which makes sun stall significantly more difficult, as the compression I mentioned earlier is no longer possible.
So, before I left stall I attempted to make a team that adapted to the metagame, one that gave ohko users as little of a chance to make an impact as possible while still retaining at least close to the same level of walling ability.
I came up with a Fightceus and three attacks Latias team. Unfortunately though, even on a team like this designed to be as resistant to ohko as is reasonably possible, certain threats must still be checked, certain supporting pokemon still carried, and unfortunately at least half, and more realistically two thirds of a good stall team will allow a ohko user to switch in. And because of the nature of OHKO moves, you can't reliably switch in to take the attack. For instance, any rain stall team using the incredibly useful bulky kyogre allows sheer cold kyogre and fissure gastro (a legitimate threat) to waltz in.
To make OHKO a small problem for a defensive team required such changes to team structure that threats that stall usually had little trouble with started to trouble me, like common offensive combo's of two physical sweepers. So in adapting to OHKO, true defensive teams make offense even more the dominant playstyle.
I later used a rain offense team that I acheived that rating with, and found it much simpler to design a team that ignores OHKO as much as possible while putting pressure on all playstyles through niche pokemon.
Any offensive team that carries a kyogre check can still be troubled though, as bulky ogre can be incredibly troublesome for specially offensive teams, and losing their check 30% of the time without getting any damage on it in return often stops their momentum too fully for them to recover from.
An interesting team archetype I did see though was an offensive team, designed to have the advantage against other offensive teams, while being rain dependent and carrying sheer cold kyogre, with a few sweepers carrying similar checks to kyogre. Kyogre's ability to pressure stall teams, and even
switch into usual checks like gira-a and grass knot/thunder less latias seemed to be a great support, and makes for an interesting mold for future teams seeking to abuse OHKO moves.
I encourage you all to test defensive playstyles and the aforementioned combination of OHKO users and offense designed to beat other offense! I think how these pan out will be the biggest factors in the evolution of the metagame!