It's sad to hear that things like this happens. The device should be able to be identified when it's using GSM or 3G network connection; hopefully you have its product code somewhere. The thieves are most likely going to sell the phone off the black market, and the dumb person who will buy it from there can only blame himself for doing so.

Sooner or later, if they want to make profit, they will have to sell it to someone for any price. The question is how skilled this organisation is. If it's a bunch of amateurs even willing to keep the stolen phone for themselves, then either they will have to disable the GSM and 3G network connections, or they will eventually be caught if the product code remains uncracked (which most likely will be the case).

Hope you at least get your money back.