There aren't too many changes with the new WM6 SDK so the majority of the applications will work on the new OS right away without applying any changes to them.
But there is always a chance that there will be a few minor updates needed in the code to get everything working as it should. From our experience I can tell that all of our applications both for Pocket PC and Smartphone worked correctly on the new WM6 OS apart from PocketBreeze and Facade.
We located a small modification we had to implement with SBSH Facade to get it working correctly with WM6 and we also located two problems we had with PocketBreeze that were just fixed with our latest public beta build from a few days ago which will soon also be officially released as SBSH PocketBreeze 5.2.
Since in our case the modifications to get everything working as it should with WM6 were rather small we decided not to release any announcement about our applications compatibility with the new OS, but instead we will simply include a notice about the WM6 support of our applications with our upcoming new updates of our applications as they come in the next few weeks from now.
I'm guessing that PI for Pocket PC had to go through some more modifications to get everything compatible with the new OS version hence the announcement on the compatibility with the new OS version