Speaking as a history grad student, I'm not sure
admitting modern historians to the canon is the best of
ideas. The modern discipline is way too fractured into
fields - the only really askable ones would be people
like Michael Grant (ancient Rome) Karen Armstrong
(religion) or Stephen Ambrose (American) who write for a
fairly general audience. As far as others - Peter Brown,
for example, does only late Mediterranean antiquity,
and just doesn't seem to have nearly the same overall
impact as would actual figures from the period or a
theorist in a field such as the social sciences whose
ideas cross disciplines.
People like Foucault
and Said are generally considered theorists, or at
most historians of ideas. I think of them in the same
part of my mind where I store the likes of Clifford
Geertz and Pierre Bourdieu - miscellaneous "thinkers"
whose ideas transcend whichever field they actually
work in.
Brian