A customer of mine asked me the same thing so I queried our friends at Cisco. The bottom line is that Cisco works very closely with Microsoft and it is in the best interests of both parties to make CSA and Vista work. There is no timeline that has been published but Vista hasn't been out that long for business users so we might as well cut them some slack. There will no doubt be plenty of support for Vista and we should see a hotfix for CSA, if necessary, sometime in the near future to provide the necessary hooks between CSA and Vista.
I would plan on it working smoothly because both companies want to be leaders in the Security arena. What's more, as the Security Industry shakes out with mergers and acquisitions I expect them both along with IBM to be the final ones left standing.
Just my 2 cents.