I wouldn't be so sure. It'd take an eternity for us to get G4 compared to Japan if they were to do that. They've already given us the 3 Year Anniversary Law. They've given us Doflamingo Kai, the big new thing for the 3 Year Anniversary in JP. And we also get things out of order pretty frequently due to Bandai being willing to bend the release schedule for big events. See: TS Luffy's release on Global. I'd counter your statement and say that there's no way we're getting G4 on the 3 Year Anniversary, because Bandai would be delaying Gear 4th for over 6 months relative to when Japan got it. The same thing also applies to Legend Sanji. I think Bandai will simply do what they've been doing for Global on major events and improvise their own events.
Japan's 2 Year Anniversary:
Part 1 Part 2
Global's 2 Year Anniversary:
Part 1(Youtube) Part 2
Japan had completely different content to run, QOL updates, Sugofests, etc. compared to Global's, partly because most content is stunted at different rates from others, such as our only being a few batches behind JP most of the time but 4-6 raids behind, a year behind in the Coliseum, but only 1-2 months behind in the story. They turned the Rescue Ace event into our (botched) Part 1 of the Anniversary and Part 2...let's not talk about Part 2's CoC. Meanwhile Japan had a long Clash of Clashes with Raid Sabo as the centerpiece, the Ace socket book island, and permanent skillup increases. Japan's 2 Year Anniversary Legend was PSY Law, while ours was TS Luffy. At our current rate of release, I'd instead bet that we'll be getting a Legend that hasn't dropped in JP yet for the 3 Year Anniversary on Global. Or they may even hold out on the new Legend Law until the 3 Year Anniversary; that seems more likely to me.
EDIT: 6 months ago, JP got the Hody batch as we got our 2 Year Anniversary. Maybe we'll get the Nekomamushi/Magellan batch for ours if it takes us ~6 months to get to the same batches JP got?