Yes but it depends on the person at Nokia processing the rebate. If they didn't know the n900 didn't even come out till say today then they would process any rebate request with an invoice that dated before the 16th as invalid since the device was not purchased within the timeframe specified on the rebate.

All a rebate processor is going do is follow the directions are the rebate

Step 1) Was the order purchased between Nov 16th and Dec 31st?
Amazon Invoice: (if it shows the pre-order date). REJECT
Newegg Invoice: (if it shows the charge/purchase date). ACCEPT

And if your thinking that Nokia will tell its rebate processing arm (if it doesn't contract it out to a 3rd party company) that the n900 wasn't released till X date and to process the rebate regardless as long as it's before Dec 31st. Remember this is the same company that has trouble informing even it's own flagship stores and customer service when they can expect the n900.