The X-Pro1, X-E1, X-A1, X-M1, X100, X10, XF1 and X-S1 will never get predictive AF, because these cameras don't feature on-sensor PDAF. You can't predict w/o a prediction mechanism.
The X-E2 (and maybe X100S, XQ1, X20, I am speculating here) might get the feature via a firmware update once predictive PDAF has been realized in future cameras.
So far, I am not aware of any MILC that offers predictive AF. This will change in the future, because it has to.