Only information I am aware of is on the Support Website which has PDF documents on the Retirement Policy and Support Matrix.
In these documents BaanIVc4 is fully supported until the end of 2008,
BaanIVc3 currently has limited support.
No date is given for when BaanIVc3 goes onto restricted support.
The Retirement policy gives a brief definition of the different support levels.
Best thing to do would be to ask Baan Support.