I just saw that ObjectArts has discontinued development of Dolphin Smalltalk.
It seems Smalltalk is going the way of the dodo bird. Basically, we're left with a rapidly dwindling number of commercial implementations which are way overpriced considering their relatively low level of polish and functionality; and the only open source option is Squeak, which is not production-ready and never will be. Then there are various dead and semi-dead pre-alpha-stage projects. One commercial Smalltalk which stands out from the rest is Ambrai, but it is in early development, and it is unlikely a proprietary Mac OS X-only product will attract a significant base of library contributions. Perhaps Pepsi will get somewhere, who knows.
A pity, really, considering how computing might look today if things went differently in the early days of Smalltalk.
Update: I wasn't talking about popularity at all. It doesn't matter if Smalltalk isn't popular; for some reason, popular languages tend to suck (Java, Ruby, COBOL, etc.) The problem with Smalltalk is that the implementations are in terrible shape. The closest thing to a usable open source implementation is Squeak, and it leaves a lot to be desired. Common Lisp is an example of a less popular language which doesn't suffer from this problem; open source Lisp implementations are fantastic.