If Touchwiz + 4.4.x is faster than stock 4.1.2, then the final one will be 4.1.2 (you read that right)
Think of the first iPhones with little downgrade protection (last updates were mostly just stripped of features) and the later (each major version is significantly heavier... and you can't go back, although they time it so that the battery will likely be very worn by that time)!