After the teenage forward impressed again with a late equalizer against Arsenal at the weekend, the Toffees trainer revealed that the club has an option to extend his temporary stay at Goodison Park for a second season if the Blaugrana agree to an extension.
However, Martinez insists that no decision on the "special" youngster's future has yet been made.
"I'm not thinking about [extending his stay] now," the Everton boss declared to the press. "What I am excited about is seeing Gerard's potential to develop and show his best in next five months. He is such a special footballer, one that anyone would enjoy watching. He's adjusted to life in the British game and understands what is needed - and he has done that quicker than we expected.
"We have an agreement [with Barcelona] over 10 months - it would be ridiculous to sit down now about the next step. We're all happy and will leave it until the end of the season and see where we are. If he does really well, the chances of having him longer are slim."
Martinez was also enthusiastic in his praise another of his young stars, Ross Barkley, following the England international's much-trumpeted performance against the Gunners.
"He takes everything in his stride," the Spaniard said of Barkley. "He's got all the attributes to be a great player. He never gets fazed by the situation. I don't think the scale of the game affects Ross.
"He's one of those players who is capable [of performing at the top level] but it is important to measure him on a weekly basis to make sure he doesn't burn himself out."