More on the combo radio. It's called the MIRGE. (Note the closeness to merger).
Essentially, there will be a package of Sirius Everything + XM Everything for $20/mo.
The thing is, however, that most of the content is already available with the "best of" package since the music programming was merged together.
The XM guys I spoke to about it basically said they are only producing it because it was a requirement of the merger agreement with the FCC.
Also, they do not plan to sell it on retail, or aggressively market it. It will be $269 and generally just available on their web site (as well as any web-retailers that go after it, which will probably be few).
To me, this is a compliance product, not something they plan to sell much of. That said, it did win an innovation award at CES.
Some more info:
SIRIUS XM Radio MiRGE, the First Interoperable Satellite Radio | BestStuff