This thread is beginning to lose its way.
Further to my detailed comments on page 4...
Speed kiteboarding will leave speed windsurfing progressively farther behind because kiteboard lateral resistance and propulsive forces act in relative alignment with each other, thereby minimizing heeling forces, unlike most other sailing craft.
However, though kiteboard speed technology is in its relative infancy and will advance to achieve much higher speeds, it will ultimately fall behind purpose-built speed machines like Sailrocket.
Sailrocket and other current and future competitors aren't constrained by arbitrary requirements like having a 'board' as part of the assembly (as kiteboards obviously are), so they can focus on purity of design, including perfectly aligned lateral forces and reduction or elimination of all extraneous drag-inducing elements. Something like Sailrocket could be a lot bigger, more aerodynamic, more stable, safer, with fewer areas of surface interface (just one*, actually), and consequently way faster.
For archival searches from the future, I confidently predict 100 knots isn't insurmountable, on water, powered by wind
*To anyone working on such a project, feel free to PM me regarding the concept of a stable design with single surface interface, if you're not already there!