Unfortunately, no. The "Look in" entry must be a template, not any other
kind of file. Besides, the .DIC file is not simply a list of words -- it's a
binary-encoded pile of word roots, prefixes and suffixes, irregular forms,
synonyms, etc. The AutoText feature wouldn't have any idea of how to handle
that.
You can do a Google search to find other "dictionary" files that are simple
lists of words, and use the Autotextloader macro to make AutoText entries
from them (with some up-front work to use Table > Convert > Text to Table
and copy the first column to make an identical second column). It's up to
you whether this amount of work is worth the benefit.