I'm curious how the metagame is going to develop... How things are going to be initially set up.
Will some ORAS ubers drop down (at least temporarily)? Darkrai and Mega-Kang have been nerfed, and the new environment might make others less over-centralizing like Greninja and Landorus.
Will some new Pokemon be ubers instantly? In particular, Pheromosa, Xurkitree, and Kartana have immense power but a very limited movepool, so I feel like they could be left alone initially and see how players deal with the new threats.
Will some old rules still be applied? In the face of these new threats, Baton Pass chaining might not be as powerful or unstoppable as it once was. Swagger might not be so bad anymore. Maybe even Shadow Tag (Assuming Mega Gengar is still banned), seeing as Dugtrio might be around more often.
I know I haven't said much or have any kind of influence, but my opinion is that it would be more beneficial to let everything that can *potentially* not be broken in, see how the metagame develops, and test/ban as necessary. There's a lot of new things - we shouldn't be so keen on keeping the ORAS rules in place.