It's certainly possible to run a p7 at 300+ lumens on 2x 123 today, but unless it was a large light, it would be just for short bursts (heat issues) and with a floodier beam than users probably want at this power level (because of the large die and small reflector). Even with a focused reflector, there would still be the donut hole. Might be better to use a multi cree with separate reflectors.
hence why Surefire would not use it to P7's maximum potential. 400 lumens out the front would mean at least 500 lumens at the LED, driven at something like 6-7 watts(rough estimate). The KL5 of old used about that much power and heats up enough, so driven a 2x123 light at 10 watts would be inconsiderate to the longevity of the light.
I wouldn't be surprised to see 600-700 lumen 2x123 lights in a month or so, as soon as someone modifies an existing "thrower" and use a hastily developed circuit to drive the LED, but how long the light will last driven at 10w, well, is anyone's guess.
as far as the doughnut hole, the KL6s(which I believe the KL9s are designed to replace) minimized that with orange peel surface, and even in a KL4 most of the time the hole is minimal(I have had 4-5 KL4s over the years). The deep reflector of the KL6/KL9 will take care of the multi-die beam, I'm confident. Multi-cree designs are fantastic for custom lights where sky is the limit, but for a mass-produced light, I'm not sure the price will be well-received, especially one that is carefully engineered and tested.