I hope the pay per click option still stays along with the pay per action model. Not all websites have something to sell. Pay per action networks do particularly well for digital products that can be downloaded. Examples of these products will be ebooks and software. These can be tracked and so the pay per action model works.

If a website sells SEO services, how can the transaction be tracked? Maybe they could track if a form is filled, however if they use other methods of contact like a personal email, it cannot be tracked and accounted. o pay per action model may not work in all situations.

I think Google doesn't remove the pay per click model completely for this reason. Besides there are some websites which advertise on pay per click networks just to get visitors. I have seen some blog and forum owners advertise their sites, just to get exposure to their sites. Google might be getting substantial amounts from these ads and so they wouldn't want to lose this.

IMO, pay per action model is more beneficial to both the webmaster and the advertiser. First, the advertiser doesn't lose any money. Second, webmasters may actually get paid more. Some advertisers offer as much as 75% commission. Now, if one gets 1 or 2 conversions a day, that should be a lot of money. Thirdly, it would eliminate most of the MFA sites and spam blogs. This would make the web a better place for us, I hope.