I remember watching Tech TV the precursor to G4 and having the biggest crush on Laura Swisher back in 2003 (she was the Unscrewed co-host).
As for G4 coming back? Olivia Munn was that entire network. She had the "IT" factor. I remember around 2009-2010 she started missing more and more shows to do magazines and acting gigs and thinking this does not bode well for the network. They never really seemed to recover after she left.
They might do well for a niche audience or even get to the levels of Tech TV, but it's going to be a situation like when Arsenio Hall came back; a little nostalgia but it will lose momentum quickly.
If Munn is involved, they stand a chance, if not, this will be little more than a reunion.