Hi Nigel
Thanks your your words about PI

The current upgrade policy is that users will get free access to upgrades until the 2.0 release. There may be some minor upgrades, bug fixes, for 1.9.x users, but at this stage no new features will be added for them.
There is no official statement about the upgrade cost. It surely will be a fraction of the new product cost.
There is no actual schedule for this major release change... it could be somewhere at the end of 2011, at the current rate.
Right now, each cycle (1.x) takes several months, where minor upgrades are constant. If it is just a bug fix release, it may come a few weeks from the previous. If it will include new features, it may take longer.