cmacd123
Subscriber
PX (and Verichrome Pan?) may have a slightly greater chance of return, but I doubt Kodak will re-introduce any product that may negatively impact on sales of their current portfolio of films.
Out of all the films you listed, 5231/7231 probably has the best chance of return..
Verichrome pan would actually have an interesting case to be made for it, as it was really am extended exposure range film in its day, I really don't know how much practical advantage it would have compared to Tri-x, but would be ideal for the Holga crowd.
7231/5231 was great. ORWO UN54 is apparently very similar, but I would guess 5231 may have an edge on grain size. ORWO of course only attempts to sell film for Motion Picture use.