When popular sites need mirrors, we’ll just add them. NewsGator uses permanent redirects to customize the NewsGator Tips feed. It would be just as easy to use permanent redirects for mirroring.
And http may be expensive in bandwidth, but it’s easy to come by. When push comes to shove, I suspect that it will be easier to find hosts supporting http compression than anonymous rsync.
No, I think that http has staked out a prime location in the land of Good Enough. And it’s not going anywhere.