Personally I don't think so. XHTML is basically a diversification of HTML; I don't see the point in differentiating between the two so strictly as to have them in different root namespaces. If it's really important, HTML::XHTML:: seems like the best place to put it.

My preferred course of action would be to take over HTML::Table and support its current interface as a stub to delegate to a newly created HTML::XHTML::Table module. They should probably both be within the same distribution. The POD for HTML::Table would be updated to point out that this module is being deprecated in favour of HTML::XHTML::Table.

Makeshifts last the longest.