We won't commit to that, and it's better to say so than leave it open and let you plan around a maybe.
What we do commit to: eighteen months from the v2 release, so the earliest switch-off is March next year, and we have never shortened that window. You get a migration guide, a compatibility mode so you can move endpoint by endpoint, and an engineer on a call if you want one.
Indefinitely is the one thing we cannot promise, because every v2 decision would then be constrained by a shape chosen in 2019.