Welcome to FT.

No matter what they do, you can be pretty sure that AY Plat will retain priority benefits, lounge benefits and luggage benefits, because those are alliance-wide benefits, so AY does not have a say over them, really.

How many points short of Plat are you after your trip to Tokyo? It might make sense to calculate and then ponder over whether you want to transfer award points into tier points or take a trip just to get the points you need, or a combination of these. If you make Plat now, you will keep that status even if AY transitions over to Adios.

Of course, once the transition is complete, it will probably be harder to maintain that staus, but in short term, you just play by the old rules.