Adobe have got their act together: they periodically (every three months or so?) release updates for the current versions of LR and ACR that bring support for recently released camera models, and currently support the unique raw files of several hundred cameras. Each time a new camera comes out, they need to reverse engineer the raw files it generates in order to allow their software to work with these files. I'm no software engineer, but I understand that this is a time consuming task that takes quite a bit of effort for the relatively small team at Adobe who work on this to achieve. Expecting instant raw editing capability within a few days of a camera being released is simply unrealistic, but I bet it won't be too long until support for a high profile model such as the D7100 is added - I'm sure it's a high priority for Adobe.
I'm not blindly defending Adobe here, but you have to try and see things from their side. It's about time the big camera manufacturers started offering native DNG support, but Nikon, Canon, et al refuse to do this, and that means early adopters of new cameras always face this issue. If raw editing from day one was a must, you should have waited for support before buying the camera...
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