Not Forgotten (Lost songs of band featured in WWE game)

The song “Tara’s Song (Live)” was added to Spotify and then later removed at some point. This is the Spotify page that shows how long the song was (3:46) as well as the release date (October 15, 2010 - 5 whole years after Waiting):

As for the credited people on the song, Glen Sobel is a very famous drummer, and he has his discography on his website going back to 1994. I would bet that he contributed to a different song, and it got mislabelled, but not entirely sure on this… maybe it was some kind of unlisted side project. I doubt it, though, because the cover art for Tara's Song looks like it was created on that old site Picnik or something. www.glensobel.com/discography.html

Hey! So this one actually really interested me. I don't have much on the songs, but here's what I could gather on the band and the other links you posted.

After looking it up, it appears that the members were studio and touring musicians who worked in production or as hired guns for other bands. Glen Sobel has been playing drums with Alice Cooper since 2011 and Russell Ali has worked on a few standalone projects. Erik Gregory seemed to be semi-active in industrial rock in the early 2000's, helping with production for Society 1 and heading the remix of By Myself on Linkin Park's Reanimation album (though didn't provide vocals on either). Here are their discogs, with links to their Facebooks if you want to ask about the songs:

www.discogs.com/artist/1498084-Russell-Ali
www.discogs.com/artist/1263317-Glen-Sobel
www.discogs.com/artist/1091144-Erik-Gregory

Additionally, after looking into the Guilty Gear soundtrack, they appear to be sung by Matt Zane, vocalist of Society 1, who Erik Gregory worked with (he even got a special thanks in the game's credits), but it's not him. Gregory also isn't credited with any other bands or video games since then.

In all likelihood they got added to the game because of the popularity of other bands they were associated with. This happened all the time in sports games. "Forgive Me" by Versus the World from WWE 2007, for example, was a band made up of ex-members of The Ataris, but signed to a much smaller label with no regular release schedule (they wouldn't even release a second album until 2012). The songs available sound very much like independently made demos, too, and Not Forgotten is the only band not credited to a specific label in the credits, so it could have also been that Erik had ties to sound workers in video game studios through his work with Guilty Gear and Gran Turismo, and was able to get the demo for Waiting to the WWE devs to help get the band some exposure while they looked for a label. 

As for what happened to the band itself, it's probably what happened to most bands like it around the same time. By the mid-2000s, mainstream punk was leaning toward sadder, more emo-tinged stuff, and it was harder for west coast/skate punk-ish bands to find big support. Plenty of groups of ex-members from more popular bands would get together, make some music independently, but either fail to get a record deal or catch fire touring and fizzled out. It's not even an irregular thing for bands who make it onto video games. Sicker Than Others had "Face Away" in SKATE in 2011, but their only album released independently in 2006 and the band had a whole album's worth of demos that went unreleased.

The guys from the band all seem to be active on social media, though. It may be possible to message one of them to see what songs are actually theirs or if there's any more out there.