Michael, the crash documented here is *not* fixed by installing ActiveState 8.5; it is currently a problem seen with both A/S and Apple's Tk 8.5.  Also, to answer my own question, I double-checked the Snow Leopard 10.6 installation DVD and, unlike earlier releases, X11 is now installed by default.

That said, there is now some action on the Tcl front which may result in an official patch to at least prevent the crash.  If so, there may be yet another option:

6. for 64-bit installer, have the installer build a Cocoa Tk 8.5 (using the installer's existing third-party lib infrastructure) and ship with the 64-bit installer

So, at the moment, I think the best course of action is to explore the various patch options and, with more info available, a decision for 3.2rc2 made prior to cutoff.