I don't get why people who bought the I1 (like me - I have 2 now) are worried about the P3 release. The video above clears it up pretty well, as well.
The P3 is aimed directly at the consumer market and the image capability from the camera is as good as the I1, currently.
The I1 is aimed at entry level professional market and the platform is modular.
The aircrafts are quite different. The I1 gives you full 360 degree rotation from the gimbal and works independently from the orientation of the aircraft, which the P3 doesn't. If you don't intend to use this, and you're not concerned about updating the camera, you won't need an I1. Simple.
The major advantage that the P3 has over the I1 in my opinion is that it's easily repaired following a crash. The I1 is not currently.
I expect DJI will soon lower the I1 price and release a new camera. Probably selling the new I1, with the new camera at the price that the current I1 sells for alongside the reduced price I1 (to clear stock). This cycle will probably repeat over the coming years as new features are released. I'd be very happy to be able to buy the aircraft separately from the controllers and the camera / gimbal.