I'm assuming Grezzo is making this remake, like they did with OoT3D. But after OoT3D they helped out on some other games and made the Flower Town StreetPass game for 3DS I believe. Also, Grezzo is probably a fairly small operation, and Majora's Mask is a weird game, so it's impossible to estimate how long it would actually take them. But you certainly can't compare them to the original main Zelda team's timeframe of making Majora's Mask back in the day.

Theyve spent all this time trying to fix Great Bay Temple =P

2 or 4, probably 2

The team played the wrong song of time actually.

I go with Option 2.

OoT 3D helped the 3DS to become such a success it is today. So maybe Nintendo thought to remake MM, too so that more people will buy a 3DS. The team started working on the new project but the 3DS became a success anyway. But then Nintendos Wii U wasn't the great success Nintendo expected. So they decided to concentrate on Zelda games for the Wii U. They worked on WW HD and more people started to work on the next Wii U Zelda. MM wasn't the most important project because Nintendo needed and needs games to help the Wii U. That's why it took such a long time for MM and it wasn't necessary to hurry up because the rumors and the growing hype about a MM Remake were the best advertisement and a sign that the remake will sell well anyway. Anytime.

http://www.nintendolife.com/news/2014/11/eiji_aonuma_confirms_majoras_mask_3d_has_been_in_development_since_2011

Since it's been in development for so long, it must've been shelved for a while. I doubt Aonuma wanted too many re-releases clustered together anyhow. MM 3D is releasing at almost a perfect time. Anyway, if you look at the above article, you'll see Aonuma said that he didn't want MM3D to be just another remake, probably hinting new features. I think that's all we need to know.

The same team that is responsible for getting the Wii u VC games to the eshop also did the MM remake so the 2011 is probably a misprint - should have probably been 1911

Was going to say this. They most likely only started actual work on it a relatively short time ago and the first years only doing some priliminary tasks, simple as that .

I refuse to believe that. The OoT 3D remake already updated all the textures, so the difference the RAM would make is minimal. It IS possible that they had problems with motion blur, which was all over Majora.

I really want there to be additional content or a Wii U version; Majora sorely lacked dungeon content and really could use the darkest art style possible. That said, I expect the team just had other priorities.

There is one more possibility; Nintendo wants to lead up to Zelda U with a Majora's Mask rerelease for a timeline reason. Meaning Nintendo deliberately delayed the game so more fans would get something Majora foreshadowed...which could actually be really badass and justify the 3 year wait.

We don't know how MM code works in conjuctiuon with using the RAM expansion. All as we know the game crashed a lot. And had to locate and change where all the checks are. I see it as a more logical reason. If that 4 year time is even real to begin with. It's just a theory.