They have history together...
Original Hyper transport systems had the option to put a Xilinx V5 in a socket i seem to recall (some German system I seem to recall) also, it does make sense providing they have a plan. Intel seem to have done nothing with their Altera IP worth noting.
Chiplet based EPYC CPUS could easily have one/two cpu chiplet replaced with pcie/cxl based FPGA chiplets... or maybe even FPGA type fabric inside Radeon chips to allow things like video decoding and ML to be accelerated and reconfigured on the fly.
Lets not forget Xilinx's experience in SERDES, IP that is needed to go to PCIe GEN 5/6 with PAM4 encoding at stupid data rates. They already have silicon running those rates easily.
Their Vitis software does compile OpenCL into FPGA logic reasonably well, well compared to the old C->VHDL stuff that used to exist years ago it's a massive leap.
I'd have suspect more of a Merger than full on buyout however. $30B is a lot of money given the market and history of AMD tripping itself up just when it look like it's on the up..