Things are in flux, but the original statement that it's in AWS now is still incorrect. The core app (and some acquired apps) is/are still on their own gear. Moving everything from their hosting environment to AWS (if that's even what is planned) would take many years.
Not yet. I believe they will be using AWS to serve Australia and/or Brazil. That or offer completely new service built on AWS, given $400m contract. Heroku runs on AWS, but its hardly integrated with SFDC.