They'd better not kill GMail without adding an Inbox option to not show attached image previews inline in the inbox. I had to stop using Inbox because not only are these annoying, but there's no way for me to control whether my contacts (or even complete strangers for that matter) send me emails with NSFW images attached.
I like Inbox, though there are some other features I'd like to see before I permanently make the switch from GMail, but the above is a deal breaker. <me>@gmail.com has been my primary email for over a decade, but I'd have to switch to something else.
The question is not if you will move off of Gmail, but when, and would it not be better to be prepared and start the process when you're not under duress from a planned sunset?
I still have to use gmail for some things like deleting lots of messages. And lately inbox has managed to freeze my entire computer for up to 30s.