Stan is going to be a first ballot inductee in 2031. The real debate is whether Del Potro will get in. If he doesn't, then Medvedev won't either, unless he pads his resume with a 2nd slam.
Cilic would have been an interesting case if he did not have the PED issue. Without that, I think he probably eventually gets in like Ivanisevic. Their career stats are pretty much in line.