Good news came from USA / Elecraft:
The KAT500 is a new high power autotuner that is can be used with both the K3/KPA500 and all other HF amplifiers and transceivers. The KAT500 uses the same topology and high performance tuning algorithms as the popular 100W autotuner in the K3. Typical matching range at 500-600W is up to 10:1 on most bands. (slightly less on 160m and 6M). This also equates to a range of 3:1 for higher power levels, up to 1200-1500 W.
The KAT500 has a front panel SWR display and three Switchable antenna outputs. It is the same width and depth as the K3 and the KPA500, and it is just 1.5″ high.
We have the tuner the lab now for final testing and firmware optimization. We hope to have it ready to sell by the Dayton Hamvention in May, or earlier.