The ability to program channels which automatically download content as often as the user requests, check if it has changed from the content stored in the cache of the PC, and then let the user know if the content has been updated, will dramatically change this balance. The amount of content downloaded from a publisher's server will increase, however the amount of content actually viewed is likely to increase far less significantly. All of a sudden rather than caching leading to an undercounting of actual impressions, caching will lead to an over-counting of impressions. Advertisers may end up being asked to pay for banners that were loaded into a page that an end user never actually viewed. Caching is good.
Response time is one of the great challenges of the web.
Anything that assists in speeding up the user experience is good. The 4.0 browsers are about to build on this ability and more fully exploit this capability. Publishers and measurement companies need to find a solution to measuring cached content that is acceptable to end users and advertisers. One that works with caching, not against it.