I heart my iPad pro 10.5, though my usage of it is in phases, depending on the type of work I'm doing. The size is perfect.
typical uses: email, google docs, browser, reading PDFs, reading news, some tv shows for portability, rough freehand engineering design concepts in sketchbook, chatting in Hangouts, kid videos (PBS kids, Nick Jr, etc), other kid entertainment (mostly sketchbook).
Of course, more substantial work (coding, CAD, whatever) requires a real computer. Don't expect to change your whole workflow as a result of having an iPad. For me, it's more of a luxury of portability for a subset of work.
Your guess is as good as anybody's when new iPads will come out and what features it will have. Subject to those guesses, you're the only one who can decide if the wait is potentially worth it. I personally think edge to edge screen all around would be pretty nice. Button isn't too necessary anymore. I've already started primarily using the gestures in iOS that make the button unnecessary.
I would consider keyboard and (to a somewhat lesser extent) apple pencil to be necessities with the iPad pro. I always suggest to people to max out the internal storage, although i suppose iPads are not so often used for gathering gobs of photos and videos. I currently have 55GB of music and 25 GB of photos/videos on my iPad, 98 of 256 GB used. Pretty sure I set my account to sync all full res photos/vids from iPhone to iPad though.