No he is not gay, after all we just seen him kiss isabella on the lips so he is not gay.
Actually, sexuality is a fluid continuum. Elton John has kids, and yet he's super gay. It all comes down to how he identifies. One can kiss a hundred girls and never kiss a guy and still be gay.
Logically, it's a kid's show, and Disney definitely wouldn't want to go there with a cash cow franchise.
From what I've seen on the show, he's gay or asexual. The flashforward episode shows his transitional/questioning period. His entire character is based around finding things more interesting than girls.