Bigshowoff has right, they will beam content to the current satellites and it will be transparent to all of us...you will continue to receive signal, it'll just be slightly different content.
I pay for 3 XM subscriptions and 4 Sirius subscriptions. IMHO Sirius is the best. I will probably put a Sirius receiver on my SEUC anyway cause I can't take XM anymore. Trust me, sign up for a short stint of Sirius on line and you'll see what us Sirius lovers are talking about. If your over 25 years old and don't like the HipHop scene and clubbin in em' then you'll love Sirius!
It's a win win for all off us in the short term as you will see no drop in service no matter what you have. They'll have to make future equipment accessable to both satellites because it will enhance coverage nationwide. You can thank all the MoCO's (Car & Bike) for not signing with both companies. That'd be like having to buy two TV's to sit side-by-side to watch all the programs.
In the long term we could see pricing spiral out of control like the cable companies have because there'll be no alternative (monopoly) and that is the FTC's fear. Free air radio is on the way out IMHO, the IMUS thing just pushed satellite even further into the spotlight. I guarantee he will be on satellite in a year or so, they just don't want to make waves until the merger is approved or denied.
Plus just go for a ride between 7:00 and 9:00 without satellite and try and find a station with any music or with no commercials.