On Monday, I called my local store (Bel-Air Camera) to check if they had a shipment date for the D7100 but they had none. This got me thinking that there might be a delay. Also, Amazon started showing on their site that they will be shipping to buyers on the 21st. However, my local store just emailed me now and said that Nikon is shipping the D7100 to retailers today, which means stores will get them tomorrow or Friday. If you want to get the latest shipment news for your area, your best bet is to follow an active thread on the Flickr D7100 group with folks confirming shipment dates.
If you are interested in the Nikon D7100, you can join the Flickr D7100 group for samples and discussions about the D7100. I will be posting there regularly.