Quoted from CaptainNeo:

P2k didn't continue because B/W locked down so many patent rights, that nobody could use anything from that format. They locked it down hardcore knowing it was the next advanced step.
P2k was brilliant. It's real pinball in it's fullest form. Those that say it's to small, don't know what they are talking about, because the playfield is actually bigger than certain years playfields. If you put them side by side, they are the same size. Just looks smaller because of the unique cabinet configuration. It was the next step forward for new pinball. Like when ramps were introduced. that was the next level. Something totally new, that could give designers new ways to design playfields have give a whole new playing experience to the player. Like p2k did. New interactive way to design games.
In the current format, there are only so many designs you can do, before you are doing the same thing over and over. Eventually you see it all, and everything has been done, hence why, you need the next step of interaction. that's why P3 is the next place to go. allows new ways to design things. Plus the interactive toys they have introduced are already more original and unique than the stuff JJP or Stern is putting out. The base format with ball tracking is revolutionary in itself. This format opens up a whole new design aspect to pinball. Which is what we need. The ramp thing has been done to death. We need something very new.