I don't think sombra will be anything like the spy.
My favorite thing about her is how diverse her abilities could be. Like, I've seen so many great ideas. Like, she could turn allies invisible for a (very) short time, disable enemy abilities, summon hacked omnics, etc. Her ultimate could maybe disable all enemy's huds (health, ult. charge, even voice and text chat), siphon ult. charge for health (maybe for teammates?), or call down a giant hacked robot.
TL;DR Sombra's gonna be really unique, and I'm pretty hype about her.