Now to answer your question, I think the new iPad Pro's combined with the features they showed for iOS11 is a step much closer in replacing the laptop style devices. I just find it convenient to detach the tablet from the keyboard when the keyboard is not necessary, and easily slap it back when needed. Has my iPad3 replaced the functionality of the laptop in my personal use? I could say it has. All those years I have been carrying my ipad 3 more than my laptop. I use it for work and leisure.
The iPad can only be a laptop replacement when the iPad can accommodate your workflow without disrupting it (at least, not to a large degree). I can think of a number of things that I can't do with an iPad today, which basically render it useless as a laptop replacement.
- I can't run macOS applications
- I can't create and run virtual machines
- I can't use a mouse (I can do without most of the time, but not always, when I require extra precision)
- I can't use it as a development platform, partly because of the above, but also because of performance constraints
Obviously, if all you do is consume content, the iPad is great. Even if you use it to produce content, it might also be ok, if you just need it to write documents, emails, etc. For some users, like me, this is not enough though - you still need a MacBook, even if you use it for a small fraction of the time.