I know that by 2025 (their 100th anniversary), they want to incorporate the new LIFES engine in all of their integrateds. I bet the L-509z will make its appearance by then with a higher price tag to boot.
I can say that the L-507z is incredible, though. It's my first Luxman amplifier so I can't compare to the others. Who knows, I might've been just as happy with the L-507uXII.