...if the current hardware does what you want? The D100 makes great images RIGHT NOW. I've had mine since the first units arrived in the U.S., and I anticipate using it for years to come. I also have an Olympus C3040Z compact digital that I also like very much. It is certainly dated technology these days--you can get far more for the money now--but my 3040Z still takes pictures of the same quality as when I bought it. For what I use it for (garden documentation, people photos and grab shots when I don't want to carry the D100) it is perfect, and I don't feel compelled to upgrade it or lament over what I paid for it.
Bottom line...there is no "best" time to jump in to digital SLRs, just like there is no "best" time to buy a computer. The D100 makes beautiful images that you can enlarge to 11x15 with high quality. And since electrons are so much cheaper than film, you can gain experience and improve your photography very quickly with a digital SLR. If this fills the bill, join in! (Although the "bill" may empty your pocket ) I haven't regretted my choice, and even if a 12 Mpixel camera comes out tomorrow and sells for the same price a D100, my camera will still continue to make terrific images.