I'm sure they'll bring back most of the original's tracks. Too many iconic tracks ignored if they don't. And there's plenty of tracks they didn't use - remember, FF OSTs had a ton of tracks per game, often on multiple CDs.
They could also cheat and double/triple/quadruple up on tracks by providing original versions and then updated/remixed/orchestral versions of the same track.
Honestly, there are so many Final Fantasy games out there, that 200 tracks is still not enough to cover everything that fans would like to hear.
FF1-15
FF10-2
FF13-2 and Lightning Returns
Final Fantasy Tactics, Tactics Advance, and A2
Crisis Core
Type-0
Mystic Quest
Crystal Chronicles series
4 Heroes of Light
Final Fantasy Dimesions
Just the 5 regular tracks per title for all of those titles would add up to 140+ tracks. Now add in the bonus songs from the first game, plus all of the DLC, and you are already over 200 tracks.