Since your conversation with Kiril (beginning of Nov) we introduced a Calendar control for Xamarin.Forms.
Regarding the support for Windows Universal, we will start supporting it after the Xamarin guys start supporting it officially (but not before Q2 2015). The controls that you can expect from our side as a start are Chart, Calendar, ListView, SideDrawer.
Apart from the Windows Universal support, we usually release updates for UI for Xamarin Cross-Platform a few days after the respective official update of the underlying Xamarin.Forms framework.
As to UI for Windows Universal, despite the fact that we may not be releasing the UI for Windows Phone controls as Universal with the pace that one might expect, we are committed to this task and the platform and will expand our offering further. For Q2 we will release a Universal DataForm, ImageEditor, DataSource and Expander components. We'll also make the ListView official.