It's well known now that Asus has had an odd relationship with Microsoft and Windows Phone 7. The OEM was committed early on to make a Windows Phone and to be one of the first to market, yet they seemed to have pulled out, nearly disappearing form the scene. Forbes has a recent interview Benson Lin, Asus' corporate vice president and the general manager of its mobile devices unit, where details are finally shared as to what happened with Asus, Microsoft and the E600.
In short, Asus was constrained by their Garmin partnership (which eventually soured), limited production ability, little access to the U.S. market and essentially being hesitant on whether or not WP7 would be supported by carriers and more importantly, consumers. So they did get cold feet. The reason why the Asus E600 even exists is because Asus went to production and made 5,000 of them before pulling the plug. Now those phones serve as developer devices by circumstance, but not by design.
Regarding their future, Asus is using Mobile World Congress to evaluate whether or not to jump back onto the Windows Phone bandwagon. That's actually not uncommon as we've heard in back channels that MWC is where next year's deals are all made--where people place their bets on new technology. That's why the Nokia deal is so important as we're hearing carriers are ecstatic over the partnership. That gives WP7 a lot more momentum going forward and while Asus says that match up won't have an effect on their decision, we can't but think that it will.