Joe Belfiore has just announced via the Windows Phone Developer Blog that the Windows Phone Marketplace is being enabled in 23 new regions. This won't be effective immediately, but in the coming months the Marketplace will be available to publishers and consumers in the following regions:
This is part of a bigger move by Microsoft to get Windows Phone into "high growth" markets, and is accompanied by the official announcement of the low-cost Nokia Lumia 610 device.
He also goes on to say how much this actually effects publishers:
In terms of actual potential app customers, the addition of new price points and customers in China and the other new markets represents a near 60% increase in the total addressable market for Windows Phone. I told you it was a big step!
Next up is a new WP7 SDK update. The technical preview of the new update has gone live and will allow developers to test out their applications in the emulator which now supports a mode where the device memory is limited to just 256MB. This will allow developers to ensure that their apps work as expected on low-cost devices before publishing to these new markets. Developers can also opt-out of providing support for the new phones, but by default are automatically opted-in. Although there is automatic opt-in for this, developers will still need to update their apps to select the new markets to publish to.
The team used feedback from users who had opted-in to determine how much memory current WP7 apps were using, and if they would run with the new memory limits. Only around 5% of the current apps failed this test, and the developers have been contacted. So the good news, is that unless Microsoft has reached out to you, chances are that your app will work as-is.
Source: Windows Phone Developer Blog