It's actually 9GB available. Does it look like games are suffering now? We are pretty much into 3rd generation of games, look what Halo 3, GTA 4 (when released), PGR 4, Mass Effect, Rock Band, Guitar Hero 3 and the other 20+ games that are coming out/out do they really look like they are suffering from compression in full HD?
Blu-Ray is just for laziness to developers, MS has some awesome compression tools (for on the fly processing etc) and low Dashboard memory footprint that Blu-Ray is not really necessary for games.
Hell what 2 games on the PS3 have said they needed Blu-Ray? And there mainly for uncompressed cut-scenes and languages files. Wow were really missing out on that in the games now arn't we, I don't think so.
If it does become a problem it will go multi-disk route, but I can't see that for a long time, just look at GTA 4. I'm not dissing the PS3 I've ordered one for me for Xmas, I just think Blu-Ray should be left for movies because that is all it's good at.
For insprition
http://www.theprodukkt.com/ look what you can do, fit a whole 3D shooter in a 64KB memory footprint, who needs blu-ray!