It's a thorough overhaul and it's due out this Fall
Metroid: The Return of Samus is often heralded as a classic – it even got a fan-made remake last year, which Nintendo swiftly shut down. Now, everything is clear: Nintendo, with the aid of Spanish developer MercurySteam (Castlevania: Lords of Shadow), was working on its own version: Metroid: Samus Returns for the 3DS. From the looks of it, it's gained much more than a subtitle edited for an active voice. It looks like a wholesale overhaul, rebuilt for 3D hardware, and redesigned with all-new items and abilities for Samus.
It's due out for 3DS on September 15, and, hopefully, someday not long after for Switch.