It is an improvement compared to HTTP/1.1, in that it allows for opportunistic encryption, and it is those connections that can be cached (or if you so prefer, snooped). This will still make it harder for NSA and similar agencies to do mass surveillance without traces. They would either have to insert their own certificate, or get the private key from the ISP. That is far more difficult to do in a covert manner. This alone makes HTTP/2.0 an improvement.
For American ISPs yes. For ISPs in some allied countries, probably. For all ISPs in every country in the world? Unlikely. And furthermore, that would require a nationwide (or worldwide) scheme where NSA gathered or issued keypairs for every certificate at every ISP. That is much more expensive than just tapping the lines, which is some of the point here, and some data probably would even be off limits. It would also be hard to keep an operation like that hidden, as they could for many years with the current methods.
I have no illusion that NSA can be stopped if they target someone, but it should be possible to make it impractical to just tap plaintext from the internet backbone as they do today. If data generally is encrypted _unless_ they do MITM attack it will be too expensive to just collect everything.
This is of cause not enough in itself, but it is certainly a step in the right direction.
