This is intentional, because adding a new arch means some overhead we don't want to add when people don't use i386, which will be the majority by now.
If you are using a 32bit app, adding i386 is a really easy task. And the new Skype client for Linux also supports amd64.

Patch works here, please test for any issues! :-)

Patch for this is on its way to out daily image builds.

This should be fixed with today's nightly builds - d-i wasn't copied over to Tanglu 4.0 (Dasyatis kuhlii) corectly, so there was a kernel version mismatch.
Thanks for reporting the issue!