V.W.
I have heard of it taking a while. I wouldn't worry too much. Certainly ask the dentist at his January appointment, but I wouldn't rush to make an EXTRA appointment just for this.
My daughter is 11 and has been slow to lose her baby teeth (they came in pretty quickly when she was a baby--- well before she was one). She had 4 pulled this summer per recommendation from the orthodontist, to hopefully stimulate her permanent ones to move up and come in. So far, they have not. It' been 6 months now. Not really a surprise, but, during that time, she has also lost 3 other teeth on her own. 2 of them on the same day. 2 of the three came in fairly quickly. One of them, we are still waiting for, and it has been over a month now. I'm not concerned though. I know they are THERE.... seen them on the xrays. :)
Ask the dentist to allay your fears, but don't worry. I'm sure everything is just fine.