Does Tcl still fit on 16-bit microcontrollers?

No.

That's not the whole story, though:

  • Jim is a very close relative of Tcl; its current size, as of spring 2009, appears to be around 80 kB;
  • Tcl as recent as 8.0 might have supported old Windows [these are matters of fact that can be researched and documented]; be aware that much or all of what is required to build old versions [document] is (readily?) available online [document]; and
  • "Small Tcl" has more on the subject.