The new icons all seem to point at a One Piece mobile game or something.
Last time I remember a generic smartphone being prominently featured in a Japanese game teaser, it ended up being a PS3 game (one of the Compile Hearts dating sims, sorry).
That could be the case or it would be something like Steins;Gate that prominently features phones...
But the news update that came along with the teaser site pretty much confirms 'mobile'.
『カウントダウン』is next to the update.
Interestingly enough though... it went from iOS/Android to their icon for 'Other' in the last few days. Their Newsbot has 'mobile / PC contents' or 'モバイルPCコンテンツ' next to the Other tag.