It looks like the Spring ’09 Release Notes have been published. This is your best source for exactly what’s coming in the next release and any caveats to it. You can see the rollout schedule on the Salesforce Status page if you want to see when you will be getting this release in your org.
The Spring 09 Maintenance Schedule is published. Also, if you want a sneak peak, go ahead and checkout the pre-release blog post from Salesforce that provides information on an upcoming webinar, how to get a pre-release demo org and links to ideas being deployed in this release.
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A nice feature was recently tagged as coming in the Spring ’09 release, Email to Case Agent Built in Salesforce. Finally, this means companies can run Email to Case without having to worry about managing an agent to run on a local system.
Email to Case is a really nice feature. It’s biggest drawback has been the requirement to host an agent yourself to monitor an IMAP inbox. This is what stopped me from using it. With the new feature, I am likely to start using it for email support of my products.
If you want to follow what’s coming in this next release, use this RSS Feed.