i think it will... it's mainstream recognition... you might hear final product on your local FM stations saying "these guys will be playing at this summer's Ozzfest, check them out" could expand their fan base by probably 1000 listeners between live performances and possible radio plugs.
I think they might only get a dozen or two new fans from the shows because most people are there to see someone in particular. If Ozzfest had Nevermore, SYL, and Biomechanical on stage 1, I'm going to see them, I really dont give a shit about the bands playing stage 2. So I think a majority of people that are NOT there to see Nevermore, WONT see Nevermore, or just wont give a shit.
but thats just my shitty oppinion.