Messi's per game goal ratio is already better than Ronaldo's, so even in goal scoring which is supposed to be his biggest (and only) strength, he does not have an edge over Messi.
In terms of playmaking, creativity, dribbling skills etc, there is no comparison. So, it is naturally much more likely to have a Ronaldo like player in the next 10-20 years than Messi as being a consistent top goal-scorer for a long duration of time is not enough to be comparable to Messi while that is enough to be compared to Ronaldo.
If anything, it would take a long long time to have another player with 7 Ballon D'or, 6 Golden Shoe, 8 Pichichi, 4 IFFHS Best Playmaker , 5 international tournament MVP awards, all records btw (quite possibly, never).
Also, there are at least 10 other players who has better per game goal ratio than Ronaldo in international games, even Lukaku has similar (or higher) ratio to Ronaldo..