(Update: Adobe's representative on the W3C HTML5 Working group, Larry Masinter, appears to be a crusty straight arrow, whose objection was aimed at ironing out procedural kinks rather than any substantial delay.)
Prince McLean writing for AppleInsider, thinks Adobe is attempting to sabotage HTML5, because it threatens Flash. Maybe, maybe not. It might still turn out that they have a perfectly good reason for delaying the latest release that has nothing to do with its potential for undermining Flash. (Daring Fireball has a brief note on the subject, which points here.)
A little digging shows that Adobe makes Flash uninstallers freely available. Actually, I'd already done that search as I'd just decided to uninstall Flash myself, rather than install an upgrade that was necessitated by yet another security issue.
Having done that uninstall, I see that the absence of Flash really does leave big gaps in many web sites, including at least a few Mac-centric sites that have no excuse for not knowing better. I've decided to continue to live with this inconvenience, at least for awhile, if for no other reason than that, without Flash, Safari flies like a jet on afterburners.
I'd suggest downloading the uninstaller for your system, whether you intend to use it (now) or not. That way, if Adobe ever decides to pull them from its website, you'll still be covered.
If you go ahead with the uninstallation, you'll be adding your voice to the chorus that's asking web developers to get off the Flash bandwagon.