Dave Smith and Sequential have never, to this date, released a real “replacement” for any of their retired synths. The Evolver is still waiting for a replacement (no, the P12 is NOT it), the Prophet 6 by no means replaced the Prophet 5… the closest thing to a true replacement they have is the Rev2 replacing the '08, but even there you have people who will tell you flat out they prefer the '08 (or the Rev2, depending on which features and aspects they consider most important). Replacement isn’t their gig - doing new stuff, trying new things that build on, but in many ways go a completely different direction from, their past - that’s what they love doing.
I kinda see these synths as: “if you like it, get it, you won’t find better sooner (or even later)”. Each one is a one-of-a-kind offering.
I think the P12 is likely to remain an absolute classic for sound designers and people who are tired of the same-old sound and already have vintage and subtractive and dedicated-FM digital synths and find some joy and beauty in the unique (and admittedly quirky) architecture of the P12. Is it a desert island synth? I think so. Maybe not your one-and-only, depending on your joys, but holy heck is it a swiss army knife of possibilities that a huge majority of other synths can only hint at.