Will it hold? Probably. Is it a good idea? Probably not.

Good screws to attach one side of the mounting plate to a stud will definitely be enough to hold the weight of the tv and the mount. That said, if you ever adjust the tv, that will put a lot of pressure on the side that is only attached to the drywall. Even if you use drywall anchors, they're not meant to support weight/force in that way. The drywall will get messed up, the mounting bracket could feasibly bend given that it's mounted securely on one side and not the other.

That's kind of the worst case scenario. I would go for the peace of mind and install blocking that spans the studs which you can attach the mount to very securely.