I think it's a bit naive to believe that guitar heroes can bring the interest for the guitar back. People look back at the guitar heroes time with a nostalgic fondness for a time that doesn't exist anymore. This was already visible in Wayne's world and became more than obvious in school of rock. Guitar-heavy rock has become a geek genre. Pop has moved on.
There are obviously various reasons for this:
1. Technologically the instrument ran its course. While the tech was still innovative in the 90s with the new digital effects, it hasn't changed much in 20 years.
2. Electronic music however has brought in a lot of new sounds that gave pop music a fresh start in the 2000s
3. People seem to be more interested in 2 things: dancing and lyrics. You could write songs with totally inintelligible lyrics and a good solo, and you'd have a hit. I don't think that's true anymore. Similarly a solo kind of ruins the dancing.
I think die hard rock fans need to get over it, guitar heroes are not coming back any time soon. I don't think it means the electric guitar is going to die. It still is an amazingly cool instrument. But, it means that your average kid may not want to try to play that "ten years after" intro anymore.