I was told DeWalt was dropping the 18v line as well, by every competitor other than DeWalt. I contacted DeWalt directly and said although they were upgrading their tool line, the 18v was in fact getting upgraded, but the batteries will be available for years. In fact, I just purchased a new DeWalt hammer drill with a different battery configuration, but it now allows both the new and old batteries (both black and yellow bases).
They do now offer a lighter Lithium battery type which is pretty slick, but just like computers, cell phones and cars, the minute you buy it, there will be something better just behind it.