I would imagine so, eventually. It's good for the company (as far as money is concerned) to release the basic Wi-Fi Kindle Fire and then release one with 3G at a later date. Don't expect this 3G to be free like the others though. The Kindle Fire does so much more than the other Kindle's and would use much more data. I can't imagine Amazon fronting the bill for hundreds of thousands of 3G devices like the Fire.
I just got tired of waiting. Wi-Fi is a connection too slow for me, so I don't plan to have it anytime soon. I already have my 3g connection for my iphone. So, I'm finally dumping the idea of getting a Kindle Fire and move on to an ipad. Sad. :-/
I have a kindle keyboard 3G and am getting a Fire for things that the 3G can't do well- Magazine subscriptions, Video, MP3s. I am going to use the keyboard one for books (seeing as I love the e-ink way better than a touchscreen read). I couldn't pass up on a 200.00 tablet for streaming video and music ;)