I just found this article by accident, and haven't seen this information widely publicized:
There won't be a BaseX version of 8.1i. However, BaseX customers still in-warranty will be offered an upgrade to full ISE Foundation for $1495. Alternatively, they can transition to WebPack 8.1i with no loss of functionality.
WebPack 8.1i will still be available at no charge, and will have all the features that BaseX had. In particular, it will support all the devices formerly supported by BaseX, and will also now include the FPGA Editor, ISE Simulator Lite, and CORE Generator.
Disclaimer: that's just what I found in the article, and I have no idea how accurate the information is.