The dude in the Smile video was damn near spot on...from his face, to his facial hair, to his bottom teeth.
There's no way in hell that could be Pac. 'Pac would be 38 years old this year...he wouldn't look like he did back then.
And like Mark 7 said, Pac wouldn't have been able to stay silent this long. I remember being with Digital and Atron Gregory, and Atron kinda joking about the rumors that 'Pac was still alive. 2Pac was wild...he wasn't about to disappear and let all this shit go down if he was still breathing.