We looked at new outlook a year ago-ish. It wasn't a standalone application, it was the Outlook Web HTML app wrapped up in a front end that would run locally. However, if you wanted to do anything besides start it up, say send or read emails, it was online only, with no local cache or storage. It also didn't do IMAP, POP or SMTP. I don't know how much it's progressed since then, because it was pretty much useless as a business tool, for a company that heavily uses the features of real Outlook.
The cynic in me says that all this is intentional. Switch people to new Outlook, force everything to upload to the cloud, and because there's no user-accessible export-to-pst facility, you're locked in. You want to keep your old emails, keep on paying the MS tax. Want to keep your old Outlook add-ins working, shame, you need to get the authors to pay a developers tax, and buy another license. Office 365 already reduces your "Security Score" if it detects you are using Outlook add-ins, if you tie that in with Insurers who are already asking for copies of your Office 365 score now, in addition to PCI DSS conformance etc for cyber insurance purposes, things are about to get expensive. You want to maintain your insurance? MS Office 365 all the way, with approved add-ins from licensed developers and a whole range of additional licenses.