The merger deal specifies that each XM share will receive 4.6 shares of Sirius once the deal is consummated. While regulatory approval is in hand, Sirius and XM have not yet consummated the deal, and until they do, XM shares will still exist.
In my opinion, Sirius and XM likely have a few financing items to accomplish over the weekend and on Monday, before they can get down to the proper authorities to set the deal in stone. This could cause a bit of a race. Sure, the NAB or another organization can try to throw a wrench into the works, but most agree that such an effort would be futile. Sirius and XM will be doing everything they can to get this deal finalized.
This could give another day or two of trading. Readers will likely see some roller coaster trading as shorts unwind their positions, those on the sidelines try to get a quick play on the spread, and the companies and organization jockey for headlines. Through all of that, what investors need to remember is that the merger has received regulatory approval. No matter what your trading strategy, this fact will remain constant until the paperwork is finally filed.
Position: Long Sirius, XM.