Well I see the root cause. My audio drivers are 24 bit/48K in SONAR (ASIO, Presonus 1818VSL) - When I set up to use 24 bit/44KHz instead, everything sounds as it should between the soft synths in SONAR and and instruments (or softsynths) in Notion 4. So this appears to be an issue where the Rewire driver itself (either in Notion, or in SONAR or maybe as supplied by propellerheads) assumes/insists on running at 44K(?).
I have several older plugs that are 32 bit rewire, but nothing else beyond Melodyne Editor and Notion 4 that are Rewire 64 bit.
If anyone is using Rewire 64, are you seeing pitch issues if you are using audio driver settings other than 44K?
Meanwhile I will report this to both Notion/Presonus and CAKE to see where it goes.