There are many ideas springing up concerning what AdSense will look like in the future and how the system will change as opposed to what it is now.
Firstly, it's clear that targeting algorithms will become even better and more powerful then they are now. This has clearly been seen with the Google search engine itself over the last few years and it should be of no surprise as this happens with AdSense. Advertisers will appear in more appropriate results and those advertisers who manipulate their content to allow high paying keywords to appear may struggle to do this unless it is actually appropriate to their content.
Another thing which is bound to happen is more protection for AdWords advertisers concerning click fraud. Google acknowledges this to be a very key issue that it needs to address as quickly as possible and there's no doubt it will happen as fast as possible. At the moment those who have high levels of traffic, can easily disguise IP addresses and increase CTR ( Click Through Rate).
Google is always keen on improving its products and this has been seen before in AdSense. The search engine company has introduced site-targeted AdSense CPM, "smart pricing" and domain blocking and there will probably be improvements that have already been added by other similar sites.
One such example is the option for the advertiser to have more control over where the content is being displayed. This could mean blocking your site from displaying on several addresses that host AdSense banners.
Another idea that has been advanced is that Google will integrate AdSense in other forms of media like newspapers or television and so on. While this might seem to be more on the science-fiction side of the facts there's no indication that this might not happen.