Final Fantasy III, Final Fantasy IV is a port of the remastered DS version of the game (which is where we got the image to the right), featuring a full 3D world and 3D characters models. The game will feature new touch controls and fully voice characters. The game also has new difficulty options both for those who want an easy road, and those who want a real challenge.
The price hasn't been announced, but given that FFIII still costs $15.99 for Android or iPhone and $16.99 for iPad, that seems like a good starting point for what to expect.
If you're a fan of the series this is good news, not only because you get to play an updated classic on your mobile device, but because it brings us all one step closer to a new release of Final Fantasy VI, which is arguably the best of the classic series.