MacGadget.de (German) reports that MacBook Pro upgrades could take place as early as this week. Expected updates include Core 2 Duo upgrades as has long been expected as well as larger drives, FW800, and upgraded DVD drives.
Meanwhile, product checks indicate that several European hardware distributers "ran dry" of MacBook and MacBook Pro inventory several weeks ago.
Rumors of MacBook Pro upgrades have been ongoing for weeks. The last MacRumors.com reported rumor from MacGadget.de comes from an iBook update prediction in 2004. That rumor turned out to be true.
Update: MacScoop claims that MacBook will see updates in 10 days.
Update 2: New Page 2 Rumor claiming Tues Oct 24 is the day.