Time based arrival spacing is on the horizon for mixed mode operations. Personally speaking I'd like to see it even earlier than planned.
Aircraft touchdown times are easily predictable, and accurate, with PRNAV approaches and "live" weather.
Artificial Intelligence can also add to the accuracy, using airline/aircraft specific data to predict touchdown time and alert approach controllers if the time-based separation required by the tower controllers is being eroded (or, is being stretched = inefficient).
IMHO it's high time that this technology was employed at mixed mode runways to increase airport efficiency.
(Bug bear of mine.)