Hi gemmasan - I feel your pain (and understand!). Btw, do note that the versions are 0.6 and 0.7! We haven't reached "1.0" yet! Some quick replies; others might provide a different perspective:
Are the plugins being tested when a new version of the core system is updated?
No. There is a reason why they're called "Third party plugins"! The dev team will ensure that the centrally maintained plugins that ship with Wolf function correctly. Otherwise, it is up to each plugin dev to maintain their own contribution. Think of the many, many 3rd party browser extensions for Firefox, for example. They're not maintained by the Mozilla foundation!
This is the purpose of the beta/RC releases. It allows plugin devs to adapt their work for upcoming releases. But the Wolf community is still comparatively small, and this last upgrade almost uniquely significant for plugins. The migration from Prototype to jQuery was always going to be a big hurdle -- but there are long-term gains, as once they are updated for 0.7.+, they should be much happier. Many of them are jQuery based, and took "hacks" of one kind or another to run beside Prototype. No longer!
Also! The plans for the plugin/extensions repository is that it should be able to list compatibilities between the plugin version and Wolf versions. This should help manage expectations, at least.
Also, will there be a section on the site that will have the older versions of the cms or will it only have the latest and greatest? :\
You're always able to continue to use old versions. While we are no longer using Google Code as our development platform with the move to Github, there are no plans (that I am aware of!) to remove the old Google Code downloads.
Two quick final comments about sticking with older versions of Wolf: (1) you will be missing all the excellent security hardening features that was one of the major goals of the 0.7 milestone; but (2) you can disable upgrade checks by making the relevant setting in config.php.
Using Wolf CMS professionally and for profit? Do think about supporting Wolf financially. Thanks!