Since this does not include the URL to a full DTD, the curse of doctype sniffing sees most browsers render the page in "Quirks" or "Bugwards compatible" mode rather than "strict" mode. In the interests of making wikipedia accessible, I think it would be better to force strict mode - then editors would be more likely to notice markup errors which affect the rendering on browsers which do not correct for bad markup.
Why don't we just let the people using such browsers send us bug reports? If it ain't broke, don't fix it.
Regards,
Erik