we do not have yet the official release date for the Sitefinity 4.0, however we are talking in terms of months here. As for the releases, we are planning on having a CTP, Alpha, Beta and final release. The upgrade from Beta to final release ought to be smooth and without any complications. CTP and Alpha should not be used for any kind production or preproduction work, but more as a insight of where Sitefinity is heading.
I hope this clarifies the questions with the Sitefinity 4.0. I am sorry that we are not in position to give a more precise timeline at this moment.
the Telerik team