Microsoft, in a statement to Forbes states the the Xbox Live will be headed to non-Microsoft devices as well. Namely iOS and Android.

According to a Microsoft rep, via Forbes:
"While the Xbox Live experiences and games always work best on the Windows platform, we understand that some Xbox fans may be using other types of devices. To satisfy that need, we are working to extend a few of our Xbox experiences and titles to other platforms."
This makes a lot of business sense for Microsoft to expand into non-Windows and Xbox hardware. There's a huge gaming market thanks to the App Store and Android Market for that.

And don't say we didn't see this coming because its at least, very profitable to do so as well.

Via Forbes