According to Ben Nicholson-Smith of MLB Trade Rumors, because the Mets waited until today to call prospect Ike Davis up from the minors they have earned a full extra year of team control over him.
He will now be a free agent through 2016 unlike a guy like Jason Heyward who made his debut already and will be a free agent after 2015.
If he stays up in the majors all season long he will eventually qualify as a super-two. That essentially means that he will have an extra year of arbitration which will drive up the overall price the Mets will have to pay him. At this point the Mets first base situation has gotten so bad that they are willing to spend a little more to call him up now.
The important thing here is that he doesn’t become a free agent until after 2016.