ChipLink is indeed routed out to the FMC. The demo during FOSDEM was done with a FPGA card attached to the FMC which then drove additional peripherals.
Your speculation is quite accurate...there will be FMC expansion cards specifically built for the HiFive Unleashed that will break out most of those peripherals you're talking about (PCIe, SATA, to name a few in particular). Unfortunately we weren't quite ready to announce those details today but will be making those updates ASAP.
The reason for the large RAMs and microSD card is specifically to help software developers. That's who the board is for until we can drive the cost down even further for even more folks.
Sorry for the late response! (was out of the country)
RISC-V is a free and open instruction set architecture (ISA). People can go ahead and build open-source implementations, closed-source implementations, licensed implementations. This is very different than ARM, where you can only buy implementations from ARM, or if you happen to be one of a handful of selected companies with an ARM architectural license (which costs $$$$$), you can build your own implementation, but they still have to meet certain specifications as dictated by ARM. People can freely implement RISC-V processors, extend them, and play around with it. We think RISC-V has a big potential to unleash innovation. As a matter of fact, we believe this is the prerequisite.
SiFive has made the RTL open-sourced that went into FE310. We think this is a big deal, because other SoCs don't open-source their RTL.
Jack, SiFive