Yep, as people have already pointed out, the bootloader is locked and the phone cannot be rooted.
Given how few of these have sold, it's unlikely that there are a lot of people trying to find an exploit they can use to root it. It seems that for the foreseeable future, we'll have rely on BlackBerry to update it.
I wouldn't worry too much about the updates, though. BlackBerry continues to release security updates promptly, and they've promised Marshmallow in a month or so. This phone may never see N, though.....if BlackBerry kills hardware before then.