I love Rublev and have been following him for years - mrzz and I both tagged him as one of our favorite Next Genners a few years back. But as much as I like him, I don't know if he has the all-around game to be the "Next Gen to beat." To me he looks more like the next Berdych/Tsonga level player. Hope I'm wrong, though. I see him as a half-step below Medvedev/Tsitsipas, more comparable to Zverev (who seems to have been surpassed in the Next Gen category).
Plus, he has a real problem vs. Medvedev. 0-4 so far, hasn't even won a set.