But what is the motivation for ADS-B? Surveillance? What will surveillance mean, not so they can track you (tin foil hat style), but so they can separate you more efficiently and free up 'procedural tolerances' and route restrictions etc.
If there is airspace where better than procedural standards can be used because you can now 'see' all the aircraft it will lead to significant savings, free up many flight levels, and routing restrictions etc. ADS-B above FL290 in Oz will save the industry bucket loads when it is fully utilised.
How much will it save in the US? Bugger-all as they currently have surveillance. So there isn't the same rush there. They will eventually save by not needing to replace service all the radar heads; but the industry will virtually not benefit from reduced separation standards, routing efficiencies etc. The big debate in the US will be about turning off Primary Radar...