Maarten Sonneveld, aka "Mr. Windows Phone, Microsoft Netherlands' Mobile Communications Business Group Lead", has talked to NieuweMobiel about Windows Phone 7 Mango, among other things.
According to Sonneveld, the next big platform refresh out of Redmond's labs, can be expected to hit roughly around mid-October, which is kind of a bit off from Microsoft's press release telling us about "early autumn". Dutch language support will be included in the menus, software input (and autocorrection) but not for voice recognition -- as in Dictation support.