I predict they will merge.
A couple of weeks ago, the feed for CNN was the same on XM and Sirius (same commercials and promos, which was weird hearing a Sirius promo on XM) so I suspect they were testing things. CNBC on XM also, briefly, showed the same PAD data as Sirius' feed. (I'm a dual sub.)
So, the merging of Fox News, CNN, Headline News, CNBC, Bloomberg, Fox News Talk, etc., is a given.
I think the sports channels will also combine, though that may cause some problems.
The "right" and "left" political talk stations will also probably merge, as will the Christian talk and maybe the truckers channels.
I'd be interested in seeing if Radio Classics will merge. Both have the same name, but different feeds.
I read somewhere that Sirius was seriously considering taking the XM traffic channels because they were cheaper.
I've also noticed Sirius XM Stars sometimes plays the same show on both channels, sometimes not. Probably contractual issues.
I did notice today that "Book Radio" went "dark" for the weekend on XM as it usually does, but was still broadcasting on Sirius. That was kind of nice.