hmm... i think the PT will have so many new elements that the boxes on the right will category categories because there will be so many more new elements. Then there will be a much bigger play area, and some one will actually invent a working virtual computer in the Powder toy that runs windows 98.
Eventually (or maybe he's doing it now), Simon will be spinning around in his chair, staring at the ceiling and thinking of what new stuff he could add to the PT that would keep the PT community from being angry that their hasn't been an update recently.
But seriously, updates will probably slow down (they kind of have already [although more content is in each one]) people will drift away from the PT, the server may slow down and eventually stop running. Simon might not renew the copyrights after so many years and like a lot of sand games, it will just fade into oblivion...