It is possible to connect M-x hippie-expand with M-x ispell-complete-word. A simple way of doing it could be to add the later function to the hippie-expand-try-functions-list

Either by using the M-x customize-variable hippie-expand-try-functions-list

or by adding the following line to your .emacs configuration:

(add-to-list 'hippie-expand-try-functions-list 'ispell-complete-word t)

Now calling hippie-expand will, as a last resort, use ispell completion to complete words.

Glorious.