Wither the Microsoft service pack

Are Microsoft service packs about to go extinct? It's possible according to Mary Jo Foley, who reports that the servicing model for Exchange Server 2007 will be delivered in 6 to 8-week increments. 

Now this development could be a big deal. It'll potentially smooth over dealings with Microsoft product support and eliminate confusion over service packs and how they affect the rest of your infrastructure. 

But it may not all be roses. Without service packs how will techies know when it's time to seriously ponder an upgrade?