Funny, I was thinking about this before I noticed this thread came up again this morning.
The creative workflow in P5 was brilliant, intuitive, and not bloated or too complicated. Way ahead of it's time.
If BandLab has acquired all of the Cakewalk code (IP), maybe they should take another look at this piece of legacy software. Potentially a Bitwig killer here, if they can dust this off and bring it up to date with a modern audio engine.
As I recall there was a thread a while back discussing the issues with moving this product into the 64-bit multi-core audio processing world. Not the least of which would require a complete re-write of the audio engine.
Several ideas from P5 made their way into Sonar, but it was never the same. As a mainstream DAW, Sonar aims to be everything to everybody, but P5 was more focused on music creation. I think that there is room for a tool like this in today's market, especially with the explosion in modern music production 'in the box'.
Maybe time for some new eyes on this???