To think these games are already 11, 12, 14 years old is insane.
Maybe waist high wall shooters arent going to cut it in 2021?
If they get around to ME4, they could easily pull a RE and switch the perspective to 1st person and basically copy that combat system but with space guns. Abilities would remain largely the same but maybe streamlined and have them be more related to healing and temporary boosts (tech repair armor and shields, biotic increases weapon damage via effecting mass effect fields etc). This way you get rid of the tired waist high shooter mechanic, and effectively have something like Cyberpunk 2077 combat but slower and less janky with melee shit. (melee stuff would be limited to pressing F when enemies get close, and avoid the jank of 1st person melee based shit altogether)
Or they could go heavier into melee combat along with gunplay and do something more along the lines of Borderlands type combat system.
Think of how sexy a ME4 game in 2022 in 4k would be with a frostbite or RE type engine? Get Wall and Hulick back to do the soundtrack, and bring back Karpyshyn for the writing and boom, you have a 500 million dollar game like ME3.
I mean fuck, Andromeda sold 4 million units.