Yesterday I was notified on starting XS that XS 4.0.10 and Xamarin.Android 4.8.0 were available on the Beta channel, and I applied the updates.
This morning, I got the same notification - XS 4.0.10 and Xamarin.Android 4.8.0. I re-applied both (in case I'd missed something yesterday).
I'm still getting XS 4.0.10 flagging as an update when ever I check for updates.
I presume that something's gone awry with the version checking in XS! One thing to note is that I have restarted XS in the meantime, but not restarted Windows (just hibernated).