Will Loma surpass GGG in stardom?

No. For one, Golovkin is a walking meme. Secondly, he knows how to market himself by appealing to the Mexican fanbase, which is one of the biggest in boxing. Third, he has one punch KO power that he emphasizes on. Forth, he fights in the middleweight division. Fifth, that smile. If this guy got a chance earlier in his career to fight elite fighters, his popularity would eclipse Canelo's. He'd be up there with Pacquiao, imo.

Lomachenko is just another Eastern European, albeit, a supremely talented one. These guys are rarely marketable, especially not in a weight class lower than welterweight. Lomachenko would have to, by some miracle, clear the welterweight division to be as popular as GGG is right now. That said, he'll still be regarded as #1 P4P soon.