Cobalt Dream, Fallendell, Sertaleina, Scaryland, Vantage, Red Comet, Fairyland, and Titan Duel are all pretty clearly popular still.
Desert Rumble, Frosty Cove and Wanderlust are a bit less liked but still moderately popular. Dune Patrol seems to be very polarising but with more likes than dislikes.
Ravaged, Crubick Plain, Intersection and Anvilwood are borderline.
Frostburn and Izki Channel are more disliked than liked, although there is still a segment of the playerbase that is not hydrophobic.
Of the borderline maps, Ravaged was already planned to be replaced by Mecharavaged. I'd like to bring Trojan Hills back in and it's a pretty large map, so it can replace Crubick Plains in that sense. Anvilwood's gimmick may be starting to wear thin and I think it has a better chance of making a return someday if it is not done to death now. I could maybe be convinced to rotate something else over Intersection.
There still seems to be some value in having a sea map in MM so we have some idea of what the 1v1 meta looks like; it is easy enough to ban a single map if you don't like water maps. Shimmershore has not been in the MM pool for some time so perhaps it gets a turn now.
With the above in mind my current thinking is:
Ravaged -> Mecharavaged
Crubick Plains -> Trojan Hills
Frostburn -> Faultline
Izki Channel -> Shimmershore
Intersection -> Random Plateaus
Anvilwood -> Doldrums