With Nokia deciding to partner up with Microsoft and jump onto the Windows Phone 7 runaway train with other leading manufacturers, one would consider the possibility that the partnership between Nokia and the software giant could enable them to receive favorable treatment over other manufacturers. At worse, this could cause issues including handset makers pulling support for WP7 or doubting their investment because of favoritism (extremely unlikely but worth the minute consideration).
Samsung have reiterated that their support for Microsoft and the platform will continue regardless of what may occur (probably because they are selling well). Chief Strategy Officer at Samsung, Omar Khan, explained in an interview at the Mobile World Congress trade show "You can continue to expect expansion in our Windows Phone portfolio." Moving onto say "Anything that strengthens the Windows Phone ecosystem is good for us," which is ultimately true.
As well adding more competition within the WP7 device market, an additional handset manufacturer could well increase developer and carrier interests in the platform itself. For now, Samsung will more than likely sit back and enjoy the sales increase for their devices - particularly the Focus and Omnia 7.