The answer to your question is anyone's guess. US Production totals for 2008 may have already been bumped up to 20,000 units.....whether it will (can?) go any higher in future years. I think the 45,000 reservation number is way high, it might be nearer 30,000 at this point. Suffice it to say, most believe the 2008 production run is spoken for. My guess is the reservation system won't stay open forever, especially after the dealers open next year, so I'd suggest to submit your $99 to get a jump on 2009. You can always get it back if someother route to a Smart comes available to you.
As far as the Sirius radio, perhaps that might be consider an accessory (there's a separate accessory catalog) and not listed in the short factory option list.