Not releasing 7.8.316 does not make 7.8.X ready for release any sooner.
Maybe not in some pure theoretical world, but in the real world it does. There it'd be closer to this:
A) Release 7.8.316 without the fix on July 6th and then a new version with it in the August - October timeframe (realistictly speaking). B) Release 7.8.324 with the fix around July 13th (allowing for one extra week of "beta testing").
Btw, what does "beta testing" mean in practice besides the urge on the mailing list to test it? Are there many here who actually test such releases in some special way? (Personally I don't, but otoh I generally use cvs-fresh versions in my daily work, so I test it continuously.)