Given the current state of art of VHDL and FPGAs, I think that circuits and programs will walk around the networks. FPGAs are boards that can be programmed to emulate every digital circuit you can figure out. VHDL is how they are programmed.
If you can send a program over the net, by copying an instance of it in a given location, you can ask it to carry out a VHDL program, reach a particular target, access a FPGA board generate the circuit and next, ask the source to load theVHDL code.
Physical medium is most likely becoming optical or wireless, but to guys like me, it won´t matter. We will leave the information ready in bytes or whatever they will call it, so it reaches the physical medium and then gets broadcasted.