The page mentions an FMC connector for future expansion, a standard FPGA expansion interface supplying 34 to 160 10Gb/s signals.† I don't know about varieties and compatibility, but Hitec makes a great number of interface cards for it, including an 8 lane PCI Express.‡
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† https://en.wikipedia.org/wiki/FPGA_Mezzanine_Card
‡ http://www.hitechglobal.com/Accessories/FMC_Modules.htm