Good choice in choosing an Apple notebook. I am just finishing my years as a college student (1 more semester), and I have greatly enjoyed not getting one virus while everyone else gets tons of viruses.
To your questions: There are many rumors of release of updated iBooks with perhaps a new form factor (widescreen).
The current generation is good, but the biggest thing holding it back (besides the small amount of RAM that comes with it... be sure to get at least 512!!!) is its graphics card. Tiger has technology called CoreImage, and currently CoreImage cannot take advantage of the iBook's graphics card. This will mean less eye-candy in the "dashboard" and less performance if you ever do any video or image editing. Hopefully, Apple will update the graphics card to be a Geforce FX Go 5200, which CoreImage can use.
The current iBooks are 9 months old, which is the longest they have gone without a refresh. Wait until August 1st. If they haven't been refreshed by then, then go ahead and dive in!