The worse case senario for me will be to cancel 2 subscriptions, continue with a single XM subscription and then suppliment by listening with my Slacker G2. I won't cancel Sat Radio all together.
Having an XM sub with the Best of Sirius will suit me perfectly provided the music channels on SIRIUS's side makes it over to XM.
As far as Im concerned Satellite offers a lot more choices in programming then Terr. radio ever will. Plus no commercials and the big names I will never leave. I could see getting a Slacker in the future though, there are a lot of nice features to gain. Not a replacement though for Sirius XM.
I am never going back to FM radio. Ever. Even if they have to resort to having the limited advertising XM had when it first started, it would still be tons better than terrestrial radio.
You simply cannot find the type of music and entertainment you can find on SiriusXM much less whole channels dedicated to them.
Worse case scenario, which would have to be a failure on a monumental scale, I would go with Slacker. Which I am already thinking of getting because I am a Digital Radio Nerd.