every droid OS will be root-able. am i saying that it will happen with every version, no. is it possible, hell yea.
google will prob do as much as possible to guarentee that their devices dont become rooted but hackers will always find a way. Google makes it harder to root because they do not want the user's phone to break or short out or for anything to be unstable. Hackers hack device's because it is a challenge. if google makes rooting harder then hackers will keep trying to root it simply as an accomplishment.