I’ve tested Sideblog and KGArchives to be compatible with my WP2.3 test install. I will be upgrading this site tomorrow to the latest release candidate for live testing. After which, I’ll list Sideblog and KGArchives as WP2.3 compatible in the WP2.3 plugins compatibility page.
As long as I’m using WP, be rest assured that these plugins will be updated to the latest WP release unless WP incorporates similar features in the core as what happened with UTW rendering it obsolete.
I happened to browse the WP plugins compatibility page and it seems that some plugins I’m currently using are missing from the compatible list. That could pose a problem but not as critical as Sideblog. They’ll likely be disabled until their authors update them.