With our new Office integrations that we have planned for later this year (and demo'd on our webinar this morning), this functionality will exist. In the meantime, it may be useful to make use of the ability to save versions with different extensions.
For example, it is common to have many old .doc files but to want to convert them to .docx files. In that case, you should save a .docx version locally and then use the option to Import a new version in the version control dialog. Be sure to set that new .docx version as the official version and then your users can work with that one moving forward. Hopefully, this can get you by until we get the new integrations released with that functionality. Thanks for the suggestion!