I didn't see Moto X listed as an initially supported device for the forthcoming Chromecast "screen mirroring" feature either- although maybe I missed it. Hopefully it comes soon. I use the Chromecast constantly and would be all over this.
I had such high hopes for a Google-owned Motorola too.
It so sad that now for Google Motorola is not a poster child, but something that they try to forget about it.