OP, chiming in late here from a personal and company owner perspective. The O365 version will be include an update to the equivalent of "Office 2019" in the next few months; there will be no upgrade path from the 2016 to the 2019 perpetual license - full price only.
From the personal version perspective, the O365 version will include a license to use Office on a Mac/PC, a mobile smartphone, and an iPad - Personal gets 1 set, Home gets 5 sets. Each Outlook.com user account tied to an O365 license gets a storage upgrade from 5GB to 50GB and no ads plus upgrades of OneDrive storage from 5GB to 1TB.
What I'm trying to find out from my MS rep but haven't heard back yet is about the Windows version, which I use 95% of the time right now is whether or not the Win O365 suite will include Visio and Project - I'm testing the Win 2019 suite and both Visio and Project are included in the perpetual license option (this test suite is only available for commercial users at this point) but this is a big deal for me as I can ditch some or all of my Visio and Project CALs. On my Mac, I use O365 in a Win 10 VM, and, on that note...
The Mac and Windows suites do not yet have code parity, but they will around the time that Office 2019 is issued. I'd offer that you check out the Mac suite's Fast Ring option if you want to see more of what's coming - I rarely use the Mac suite but do have it installed and the updater set to the Fast Ring - the apps are currently on v. 16.16. My MS rep related to me that the fully-unified code per app will be present in the next 90-odd days - the full Office 2019 updates will likely hit the interwebs around mid-October.
There's plenty of other changes coming to O365 in the near future, and I'd offer that you check out the
Redmond Channel Parter web portal - there's plenty of in-depth content there. A for-instance is that, if you have the OneNote 2016 app installed on your Win10 PC (no word on Macs yet, and only Win10 will be supported for Office 2019), sub to O365, and haven't used OneNote 2016 (the current desktop version), a future O365 update will delete the desktop app - plenty of insights on that web site...