The following comes from an IGN interview with Yoshio Sakamoto...
On Metroid: Samus Returns being a remake
"It’s the same game. … All of the fundamental design is the same ... in that the basic map structure is all based off the Metroid II map. Basically what we’ve done is we’ve used this new technology that we have at our fingertips to just polish up what was already there and to improve upon it. Maybe the thing that felt so different was that it was in full color."
- you can leave marker points on the map and tap on points for information
On the game potentially having new content past what's in the original, similar to Zero Mission
"I believe that yes you can go ahead and look forward to some of those same experiences that you had with Zero Mission."
On adding more backstory
"[In] this game there’s a lot of background, there’s a lot of lore involved in this title. But it’s not like a novel or something. It incorporates the lore, but it’s not integral to the gameplay experience. It’s in the background more than in the foreground.
There is definitely information for the players to get that revolves around sort of the larger storyline."
On what brought Metriod: Samus Returns into development
"About the time I was looking at the 3DS and the great specs and this game and the features that it offered and was thinking to myself, 'Man, maybe this is the time to revisit that 2D Metroid game.' I had heard that MercurySteam was interested in working on some sort of Metroid remake. Not 2, but they had some interest, and those just sort of overlapped with each other."
On this being tied in any way to the long-rumored Metroid Dread
"I think it’s better to say that this is a remake, remastering of Metroid 2, a powered-up version of that, and not something to do with the other project."
On connecting to Metroid Prime 4
"This time there is not any direct connection between Metroid Prime 4 and Metroid: Samus Returns."
On involvement in Prime 4
"I’m not involved in Metroid Prime 4."
On how long the game is in development
"We started around two years ago, so it’s been about two years... It’s almost there. It’s quite a ways along. We want everyone to play Metroid this year. We would love for it to be a Year of Metroid, as it were."