Typically K2 will support the current product release (now BlackPearl) plus one previous version (K2.net 2003). This may depend on your specific K2 product licensing however.

The schedule for a next version of the K2/BP platform is unknown at this point.

Since the K2.net 2003 has been around for over 4 years, I would consider that to be a fairly reasonable timeline (+/- a year or so) for any subsequent K2 products...though K2 development teams are always busy evaluating new technologies coming out the door (Microsoft and other vendors) which may accelerate the schedule based on how such technologies may benefit customers.