Nearly everything that has to do with ads (both tracking and serving) is already standardized client side script, so it won't make much difference for publisher

Nearly everything that has to do with ads (both tracking and serving) is already standardized client side script, so it won't make much difference for publishers/advertisers. Ad agencies already want data vetted by someone like Comscore, and most publishers use tools like Google Analytics for their own purposes. I suspect those tools already account for invisible pre-rendering. This doesn't really effect much, to be honest. People who want to inflate their stats already do so by counting bot traffic, iframe requests, etc. Google's been doing partial javascript evaluation for a long time as part of their spidering.