I'm a returning player. so. I never saw Greninja get out of the game. You can still win several tournaments in standard or expanded, not as many as before.
Why do not you see it in standard tournaments? Obviously by decidueye/plume hype.
If you think it's going to be off the top deck I would not bet.
What does the new set bring to me? Not much, aqua patch or field blower I find very slow, and would use bursting balloons all day instead of choice band, although I need two turns to get 250. Well, okay, I want to use Rescue Stretcher, instead of super rod, returning a Pokemon to the hand is very tempting.
Now I do not understand why Wally left all current lists? Is not this a card that helps you against the basic GX and Eeveeolutions of the first turn?
Wally isn't in most lists because there are faster ways to get most staged pokemon set up. Usually via Rare Candy for Stage 2's or just laying down as many basics as possible and drawing into the stage 1 GX the next turn (I won't get into Forest of Giant Plants decks). Ultimately, the reason Wally isn't played is because there isn't really a deck where having a S1 set up T1 really brings much benefit. I mean, I guess you could make a case for a T1 ability lock Garbodor with a tool being pretty disruptive, but that would also completely destroy your ability to set up anything else.
As for Greninja, Choice Band >>>> Bursting Balloons. There are a *lot* of decks now that don't even try to do damage early (look up Quad Lapras or Quad Sylveon). There are also a number of decks where that bursting balloon damage actually helps them because they are running Tauros GX and all you are doing is getting that bad boy ready to take prizes. Finally, with a deck like Deciplume, they don't have to attack you to do 60 damage per turn. They just ping away at you while you sit there with your balloons. Choice Band is a clear upgrade for this deck because it allows Greninja to hit some huge numbers to take OHKOs without requiring your opponent to attack into you. There are a lot of pokemon that sit at 210 hit points which is just out of range for 2 Shurikens + the 80 damage attack. With Choice Band, you can toss down an energy and hit that 210 damage even without placing the energy back into your hand (example, say you didn't want to return a splash energy). Choice Band also allows you to OHKO things like M Rayquaza because the damage output for Greninja without a Kukui tops out at 230 with a Choice Band rather than 200 without it. That's pretty huge.
Field Blower is an obvious addition to Greninja as well (in probably a 2 count actually) because ability lock Garbodor still sees play and Field Blower is really the only way to deal with that card. It also allows you to discard pesky stadiums.
Finally, I actually use a 1-1 split of Rescue Stretcher and Super Rod. There are times that energy needs to get back into my deck and I don't want to use my supporter to make it happen.
I don't think Aqua Patch has much (if any) place in a Greninja deck. There are already a ton of struggles getting set up consistently without adding that additional piece of fluff to get in the way.