I am not sure where I should ask this, however, it does involve Xamarin. Hopefully someone here can either answer the question or send me somewhere that can.
If I create a new PCL in VS2013 U2, I can select Windows Phone 8.1 along with any other platform target except Xamarin.Android and Xamarin.iOS. Has Microsoft announced they will support this configuration? It seems like an oversight, since Windows Store 8.1 apps (theoretically equivalent to WP 8.1 apps) can share a PCL with X.A and X.iOS.