#1. "RE: First SLR, 3200 or 3100 - ISO performance?" In response to In response to 0 Fri 11-May-12 08:42 AM by jpFoto
Welcome to Nikonians. This is a terrific site with lots of information and help for both novices and pros alike.
Both the D3100 and D3200 are excellent choices for your entry into the world of DSLR cameras. I have owned the D3100 and now own the D3200 and can recommend both. The D3100 is an excellent camera and a real bargain at current prices so you can't possibly go wrong if you buy one. The kit lens, the 18-55, is extremely sharp and a bargain when paired with either of the camera bodies.
Contrary to what the fellow in your referenced article has said, and I suspect that he hasn't even handled the camera, the D3200 has higher ISO capabilities and better resolution. I've owned mine for about 10 days and have been very impressed with its performance and actually find it hard to believe that Nikon can offer so much camera for such a relatively low price. Since the camera is new there aren't too many reviews available yet, so you may want to wait until some of the credible and respected sources have had a chance to do their "hands on" reviews before you make your choice.
As for your question about how long of a time you would own a camera before upgrading, there is really no answer. Technology always gets better, but for now the sensor in the D3200 is "state of the art" for a DX camera so it could be a long time before you felt the need to move on.