During the week, Microsoft announced that Windows Phone 8 will be available in 180 countries, that's almost 3 times the current number of countries with Windows Phone 7.
Now developers from these new countries will be able to develop and publish localized/global Windows Phone apps in their local marketplace.
The current number of apps stands at 100,000, I expect this number to quadruple when Windows Phone 8 is launched and made available to new markets.
Below is the list of all 180 countries (including the current countries that it is already available in) that Wp8 will be available in.
It is important to note however that this list is subject to change prior to the initial launch of the Windows Phone 8, new countries could be added or existing ones could be removed