I would start to play now. There may be things in the next edition that you love, and there may be things that you don't. The only way you would be able to know one edition from the other is to have experience with both. Being as AW is so modular, you'd be able to cherry pick from both to satisfy whatever happens to flow better around your table.
I won't talk about what is or isn't there, you can pay a dollar for that information if you are curious. I will say that there is nothing preventing a switch from one edition to the next in mid-game, even if a playbook is gone or defunct, you just start a new playbook and move over the moves that make sense in the new edition. Even if a move triggers differently from now on... it doesn't effect the story. What I consider the biggest changes are mostly around conceptualizing AW, not really the act of playing in an AW world. I would keep to the core playbooks however, that way you don't have to fiddle with rewording anything on books that wont be under Vincent's purview as guesswork, at least during the immediate switch. I'll be honest though, I pretty much welcomed everything and a tiny amount of money to support the games development was worth it for me. I immediately put in many of the things shared behind the scenes.
All that said, AW games are a blast even if they're only one week long, my favorite games have been six to eight weeks, and the rare ones that extend longer are functional with the right group. AW moves much faster then traditional games, you'll start to see how much the other systems create lag.