A month or so after the api changes go into effect and 3rd party apps are gone. Then it will occasionally pop up every now and then when more reddit news comes out about the company.
The apps shut down on July 1, so probably a couple weeks after that.
Then one guy will show up in August, having been on a six-month meditation retreat, and will shrug and sign up on whatever Lemmy instance has survived the mid-July spampocalypse.
(Even if everything goes well, there will be some problem, because it's the Internet and there are bad guys on it.)
I don't use iPhone, so I can't speak for any of those clients. I believe liftoff will be in the play store soon for installation/updates and it will support ios as well. I've mostly been using liftoff.