Basically this topic comes up EVERY single time a console war is in operation.
The straight up answer is NO. There never will be. The arcitecture between the two consoles is far far different to each other.
The next generation of machines may be able to emulate either, or both of the machines but not in the near future.
The megadrive couldn't emulate the snes, the same way the ps1 couldn't emulate a saturn.
It would be nice, but keep dreaming
J