This (or anything else) isn't going to bring back a resurgence in Tcl use. A simple web app framework like this is something many languages have, and I think in this case it's best seen not so much about the web framework being the centrepiece. Instead, for the existing (and generally aging) body of people who have a good sized chunk of their work in Tcl, this becomes another utility to build an interface to that other code.

As an aside, Tcl was influential as a source of inspiration in the early days, ranging from event-driven programming, to web servers big (AOLserver) and small (Brent Welch and Stephen Uhler's <200 line server/HTML parser) back when "normal" was forked CGI scripts.