From everything I've heard and seen these ski's have not changed for '09 except for the graphics (with the Watea graphics getting particularly worse, while the Dyna's are similar though perhaps a bit nicer).
- The '08 Wateas seem to be pretty well sold out, while I think the '08 8K's should be easier to find (and at possibly a great price as mentioned above).
- Your question makes it sound like these skis are interchangeable. I demo'd both skis last year and found them to be very different:
- The Dyna has a metal sheet and slightly less sidecut, so it feels damper and more comfortable going straighter and faster. OTOH it doesn't feel particularly torsionally rigid so when pressed to edge/carve it seemed to want to skid, and prefers to skid/swivel in the bumps. It's decent in deeper snow though not great. Overall it seemed better suited to a more intermediate/advanced skier technique.
- The Watea is livelier/playful and far more adept at carving/edging even at speed. It's wider tip caused it deflect in bumps a bit more, but for me it was more willing to make short turns through them or anywhere else. It definitely worked better for me in deeper (though not cruddier) snow. While quite fairly forgiving and easy to ski it seemed the better suited of the two for a more advanced/expert technique.
That's my $0.02 plus the added $0.01 of unsolicited information.