Whoever the submitter is, he/she seems to have a pretty rosy view of a merger would result in. It doesn't mean that both XM and Sirius would fuse into one all encompassing uber service where you would get every existing channels for the same monthly fee. It just means that XM/Sirius would be owned under a single corporate umbrella. I would not be shocked to see increased monthly fees post-merger. One thing keeping subscription fees at their current level is the fierce competition with each other and fear that a price increase would be met with a flood of subscribers jumping to the competition.
If anything, they would try to differentiate each service in the market *even more* and remove redundancy, so to get the whole variety of channels, you would have to subscribe to both. It makes sense from a shareholders perspective; if XM and Sirius are both the same company, why spend resources having nearly identical Rock stations on both carriers? But if you put 80's and Metal Rock stations on XM and Top 40 and Punk Rock stations on Sirius, then listeners who enjoy all genres of rock have to make some painful decisions or (ideally) subscribe to both. And if you owned the entire satellite radio market, then there's no fear of your customers jumping to the competition, because there is none.