With this blog post from Jameson Lopp and evidence he found and used in the post for proving Hal Finney is not Satoshi Nakamoto, I believe that Hal Finney is not. Except if Satoshi Nakamoto are more than one person and there are other people in Satoshi Nakamoto group can do emailing to Mike Hearn.

Hal Finney Was Not Satoshi Nakamoto/. If Satoshi Nakamoto are not a group of people, but as a single person, he must be someone else, but not Hal Finney.