If price is no issue, buy VI; if you think it is too much then buy IV. The two are very similar in design. I personally don't see one being more appealing to the other. Forget III, the new armored body have got way too many new improvements over the old one that it makes III look bad.
not sure about the future of the video line, but for the movie line im pretty sure we will see two different alice - herself and the clone
executioner is quite unlikely tho. they will have to develop a new body for it, which i dont see happening...