I've switched Chrome to using Bing over SSL and it appears to work fine. As probably expected, not all Bing services work fully with SSL. For example, trying to load Bing images will work great until actual image thumbnails load.
Another reason that Bing might not have made any announcements about this is that there are still some scripts that can be loaded insecurely. Chrome by default blocks them, but you'll get a gray security badge on the right side of the address bar. Perhaps once these issues have been fixed, Bing might formally announce HTTPS support.
Another note: Because this post was created before Bing formally announces SSL support, they could switch back to HTTP only at any time whenever they wish. I doubt they would switch SSL off, but if they do, it's not like they "can't". Some folks are reporting that SSL support is not enabled everywhere, so Bing might just now be rolling this out.
