Honestly, with how bloody the original game it should have a M rating in HD - when Sephiroth slaughters everyone in the Shinra building he paints the walls with their blood, it looks like something from a horror game.
As for smoking, since 2007 the MPAA has considered smoking as a factor in rating movies, often bumping up ratings for gratuitous smoking. Since 2012 there has been a push, at least in movies, that smoking should mean an automatic R rating - because of studies linking minors seeing smoking with minors taking up smoking.
However, there has yet to be any strong push against smoking in video games (perhaps because people are still busy being concerned over violence and sex in video games). Video games seem to get away with more in general than movies in terms of violence and sex. In movies an NC17 rating effectively kills the movie and things are cut to get down R, with video games the only things which get an A for Adults Only are usually things that have straight up pornographic material or real gambling - things legally limited to adults. And the M rating seems less restrictive than R ratings since many teens can get adults to buy them M video games more readily than take them to R rated movies.
From the trailer though - it looks like they're going for an older audience with 7 (they can get kids with Final Fantasy Word and younger teens with KH). The AVALANCHE guys you see in the trailer against the wall look straight out of Metal Gear or any war game. An M rating wouldn't hurt the game's sales - so I'm not sure I could see them sacrificing anything to get the T rating.
In KH a lot of things were edited out (smoking, alcohol, guns in the Pirates of the Caribbean section - because it was a bad idea to put a PG-13 movie in a game that leans towards PG) - but that's an E10 game and making it T might hurt sales since they want to pick up younger players with the disney appeal (despite the game being a better fit for teens in many ways with all the existential angst).
I don't think having FFVII rated M would hurt sales. Look at Skyrim v Elderscrolls, the jump to M hurt nothing (though some parents wouldn't let their teens play it - which I think is silly because the stuff you know by the time your in high school is worse than any R rated movie).
But really, I just don't see how the violence in the game could get a T rating. With swearing you can have a T rating if it's infrequent enough - and as stated smoking isn't that big of a deal in game so far - but FFVII has a lot of blood.
But maybe that can argue since the original is rated T - and the remake has the same content the rating should stay?