Most likely Google will wait and see how the markets change before making any decisions. Are advertisers concerned enough about click fraud to jump ship altogether or will they see PPA as an addition rather than a replacement? Most likely both will remain side by side although most experts expect many advertisers to move away from PPC to PPA.
For some tourism advertisers the PPA action model will definitely be a better option. Resort and cruise tourism operators with online booking facilities will mostly benefit as they can run a campaign that they will only pay fees whenever they make an actual online sale so they are guaranteed to make profit or not pay any advertising fees if they get no conversions. It eliminates the risk for operators and will probably attract new customers that have previously stayed away from PPC which can be costly and ineffective if the conversions are low.
Other operators that sell lower value products and services or don't have credit card booking facilities online, such as small dive centres and tour operators, though may be forced to remain with PPC as PPA might cost more than their profit margins as competition for keywords pushes prices up.
For Google however there isn't really much risk launching PPA. It will most likely attract some new customers and if customers leave PPC to use PPA then they have kept those customers happy by offering them another option and maybe retaining customers they would have lost to other affiliate schemes. Its one more string to Google's bow and again places them at the fore-front of online advertising options.