Earlier this month reports started coming in that Amazon had lifted the ban on new international workers. Multiple threads have been posted on many worker forums confirming that Amazon has now accepted dozens and possibly hundreds of dormant accounts that have been pending since 2012.
Overall, we believe this will have a minimal impact on Mturk as a whole. For academic studies to target individual countries other than the United States and India, there would have to be thousands of new registrations and participants would have to be able to get cash from Mturk.
For people outside of the USA and India, Amazon Mechanical Turk still only pays workers with gift card credits on Amazon.com.
This influx of international workers could initially help requesters like ScoutIt aka Jon Brelig complete tens of thousands of $1-$2 per hour, but for the most part, it will have no impact on the experienced requester or worker.
Hopefully new participants studied the participation agreements they signed when the submitted their accounts for approval and understand they will not be paid in cash.