Can they do either of those things? Yes, they probably can.
More importantly, will they?
New content/features such as? It's unlikely they'll develop new content just for old worlds. Some worlds only have 30-100 accounts valid in the ranking now. They're not going to develop for such a small user base, especially as many don't spend on the old worlds and only visit sporadically.
If there are enough players on a world to have 'enemy alliances' that are active then the world isn't totally dead.
Ending a world: What about the few players still active with resources in storage? Some of which may have been bought, should they lose that?
Transferring resources between worlds would be nice though, then killing a world becomes less of a resources issue.