Anything is possible but I think they will steer clear of that market-
Price point being main issue I would not see Apple doing that-
for the most part what you already spend for a mac mini, iMac or MacBook... you could build a custom pc with more options to upgrade without having to wait for Apple to release new models or allow you to upgrade-
*edit That said I am sure if Apple offered it there are some in the Cult of Apple that would purchase it