When I saw this , I just had to laugh.
Seriously, who's going to buy the Final Fantasy XIII Trilogy if it releases? Think logically, Square Enix.
Wait, I know you're not capable of that so let me explain: There are several groups of people out there who might be interested in such a product. First, there's the long-time veteran fan, who you've long since alienated, so you can't count on any support from them. Most of them viewed FFXIII, XIII-2 and the shockingly mediocre Lightning Returns as a huge step back for the industry. A few die-hard collectors would purchase the Trilogy just as a general rule but that's about it.
Then you've got those who might be interested but haven't played all three games. Well, all they need to do is a little research, and they'll probably pass on the idea. Reviews went downhill throughout the series (as did sales) and really, they won't feel like they missed much if they only played FFXIII and part of XIII-2, for example. Lastly, there's the group that has never played any installment in the trilogy, and might find such a package enticing. But this group consists of either, A. those who have no interest in the first place, and B. those who would very likely opt to choose another game off the shelf, given the sheer amount of greats currently available.
And finally, as there's zero nostalgia behind this (as there was with Final Fantasy X/X-2 HD Remaster ), nobody is really going to care. It's just a dumb idea. But don't you worry; Square Enix will probably still do it.