not sure why you should but other people don't want to buy a new gpu after a while and stuff like that.
but how do you already know the games library of the nextbox? or if you won't get something like ps+? you talk about stuff of this gen to know what next gen will offer...
maybe kinect 2 will be something you and your family would really enjoy (i believe you have one), i have no idea but we should talk about it when we know about it.