Paul Gardner-Stephen and MEGA, museum of electronic games and art, just announced the MEGA65. It is a modern day 8-bit computer. It is compatible enough with the C64 to run old ROMs and programs, while it supports modern interfaces such as SD-cards, Ethernet and more.
The project is open source and available on github. Right now you can download an FPGA bitstream, the VHDL source and some bootstrapping programs. The plans are to build a physical machine with a proper 8-bit look and feel. That is something that I really am looking forward to.