By anyone. I believe it has to be the exact tweet provided by the link though.

OT: Almost 5k tweets down. This should be uncovered soon enough. I'm genuinely interested to see what it is, and to see why it's being revealed through the SMTIV site (directly above an ad for the SMTIV "Best" rerelease, no less).

Oh I see. Yeah this shouldn't take too long, SMTV for 3DS is my guess.

Please be right.

Please be for the 3DS, whatever the announcement is! I don't want to have to buy another console.

Is that an A?

I think the likelihood of it being for 3DS is quite high given where they're advertising this.

I'm mostly interested in what it even is. Is it DLC for SMTIV? A remaster of an old game? A new spinoff? SMTV? The broken piece kinda reminds me of SMT Nocturne, but even more grungy. 

Apparently Nintendo game magazine retweeted it.

Mmmmmmmmmmmmmmmmmmmm!

Looks like it. Though it's entirely possible we're just not getting the whole picture and it only looks like an A.

My bets are on SMT V. A remaster and a spinoff sound plausible as well. Though I very much doubt it's going to be DLC for SMT IV, it has been quite a while since the game came out (2013 if I'm not mistaken.)