I'm sure he would if he could, but it would be a tremendous stretch.
You don't have to be convicted. Gerald Ford pardoned Nixon for any crimes he "may" have committed even though Nixon had not been criminally convicted or even indicted. But, all Obama could do is pardon illegals for the criminal act of coming into the country illegally. That wouldn't make them citizens nor give them a right to be here. They would still be subject to deportation. Since no one is being prosecuted for such an offense such a "pardon" would be meaningless.