Not a chance. They'd lose 99% of the serious developers. I couldn't imagine doing app development without 5 terminals, photoshop, xcode, and a web browser open at the same time; running git, grep and a series of shell scripts invoking all kinds of unix tools and imagemagick and ffmpeg and so on. If iOS can ever deliver that then we've gone full circle back to macOS.
To be productive you need big monitors and overlapping windows and terminals and drag&drop, and beyond a physical keyboard you need a pointing device that doesn't require you to cover the things you are looking at with your fingers. And nobody wants to sit for 8 hours a day stretching their arms out to touch a monitor or crouch over a tablet on a table.
The way you imagine productivity works like that. The past is funny, because it seems like that way worked for us and so it should be good enough for anyone.
As I watch my kids using iPads regularly, I realize they don't really know anything at all about a 'desktop' or why its so complicated. We can argue well they need to learn how a computer works, its important etc etc. Maybe they don't for the most part and could just build on top of our knowledge base to get to the next place. We are the old people telling kids to get off our lawn.
That would limit their dev environment to making native apps for three device classes (tablet, phone, watch). It would neglect their massive presence in the web dev community among others. Along with probably eliminating them from the university student market (as much as they're in it now). And definitely eliminate them from the enterprise market (I can almost, but not quite, get one now at work, it'd be gone for good if I only had an iPad option).
iPads make good, portable devices for a lot of things. But it'd be a foul up of epic proportions to try to move their laptop/desktop users to it.
To be productive you need big monitors and overlapping windows and terminals and drag&drop, and beyond a physical keyboard you need a pointing device that doesn't require you to cover the things you are looking at with your fingers. And nobody wants to sit for 8 hours a day stretching their arms out to touch a monitor or crouch over a tablet on a table.