Sorry, but as a paying customer I find your attitude seriously lacking. The question you guys at Sencha should ask yourself is: Can we use TypeScript to benefit your customers and if yes, is the effort worth the result.
I really think at least for your customers that use Visual Studio 2012, providing TypeScript definition files would give your customers a much better tooling experience with little effort and create an additional selling point.
I'm probably walking on thin ice here, but I honestly think official typescript support would detract from the product. It would needlessly complicate things with little benefit and then you would have to compile before your compile. They would also then have to provide support for a third party language. It is much better driven as a community project for people who absolutely must use Typescript.
The best way Sencha could service its customers who prefer to work in Visual Studio would be to provide an intellisense plugin or other tools to aid with the development of Ext in Visual studio, not another language.