G Package clients should see service start to roll out in April or May, depending on which release schedule your company prefers. Here’s the Complete list of supported filetypes, according to Google:
Unless Google has to pay Microsoft to get this functionality for a certain reason — this is something which could come to stop users, also.
Powerpoint files: .ppt, .pptx, .pps, .pot

Excel documents: .xls, .xlsx, .xlsm (macro enabled Excel files), .xlt

Assessing Microsoft Office files in Google Docs is a Nuisance. You’re able to view them , but you’ve previously had to convert them to Google’s format until you can edit, comment, and collaborate inside Docs. That’s about to change: Google just announced that it is adding native support for Microsoft’s Word, Excel, and PowerPoint formats — like .docx, .xls, and .ppt — that will allow you to do real-time cooperation in the industrial variants of Google Docs, Sheets, and Slides.

Word documents: .doc, .docx, .dot
Yesterday, Google announced it would let you create and collaborate on Google Docs, Sheets, and Slides files via Dropbox Business as well.

Again, we are referring to the commercial versions of those apps right now, namely G Suite, so this is something your company’s IT admins will be enabling (or disabling) in the brief term. It’s not something that’s necessarily available for all Google Docs, Sheets, and users that are Slides yet.