Well the Foo Fighters have said that they plan to be recording their next album in the first quarter-half of next year. Release wouldn't be long after that and thus a tour. I don't know much about Soundgarden but I try keep up with the Foos, can't see it happening with Dave.
The connection there makes sense. I suppose they might consider getting some relatively unknown drummer so there's no clash of egos when/if Matt Cameron returns.
Here's a half hour long Swedish TV program about Black Hole Sun (and a bit about Superunknown in general). Features some interviewing of Chris and Ben... and also the producer. So it's a Swedish show, but with quite a lot of English in it, if anyone is interested :)