I have updated tcl/tk to version 8.4.x (currently both ebuilds are masked in package.mask). Looking at your ebuild, I suspect, that it can stop working or block. Please test it with new tcl/tk, and fix it or close bug, if it works. For examples of tcl/tk version detection see /usr/lib/tclConfig.sh, net-analyzer/rrdtool or media-sound/waif
It seems, that tclx-8.3 can be built against tcl/tk-8.4.2. I have added tclx-8.3-r1.ebuild, which does it, because tclx 8.4 is not yet officially released (only in CVS).
Sorry for not replying earlier, I didn't receive any email about this bug until the last message (?). I've tested the updated ebuild, it seems to work fine.