I had a conference call with Xilinx before announcing this project and they agreed to transition the VCU1525 into a production product for a slightly higher price; the production version will be released in June/July, in much higher quantities.

Regarding the question about bitstream compatibility, the answer is no, a bitstream built for VCU1525 will not work on the XUPP3R.  The clock & USB UART are on different pins, so I must 'build' two versions of the bitstream, one for each card.  Although the change in the code is tiny, it still takes the tools 5+ hours to re-run place & route, with multiple runs needed to get a success.