I think we might be looking at something like Skyward Sword HD for Metroid Prime 3.
It won't have much of a visual improvement outside of resolution, texture filtering and maybe textures, but will be a high effort deal due to the work needed to both translate the controls fully to button and analogue and mastering the pointer controls in gyro.
Prime 2 I really hope is at least a Wind Waker HD effort, as in all new textures and lighting.
I don't think we should expect visual remakes like Prime Remastered for the other 2.
At least not if they're coming before Prime 4. If they're 2025, then sure, it probably means the team that took over the games after Prime Remastered was done in 2021 had time to use that engine and assets and textures on 2 and 3 and remake the games.