expect links with libtcl8.5.dylib:
$ port installed expect
The following ports are currently installed:
expect @5.45_3+universal (active)
$ otool -L /opt/local/bin/expect
/opt/local/bin/expect:
/opt/local/lib/libtcl8.5.dylib (compatibility version 8.5.0, current version 8.5.13)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 169.3.0)
Now that tcl has been updated to 8.6.0 libtcl8.5.dylib no longer exists; the port needs to be rebuilt to link with libtcl8.6.dylib instead.
We could also use this opportunity to update expect to use the tcl 8.6.0 sources.
Unfortunately expect does not build with tcl 8.6.0 (regardless of what version of tcl sources it uses). Attached is a patch to update the port, and a log showing how it fails to build.
libnewt is a different port maintained by a different maintainer and probably needs a separate ticket.