I think Apple's "laptop replacement" vibe is just some good marketing. If it really was a laptop replacement for everyone then all the dev's in Cupertino would be using them instead of their MacBooks! This is just some eager marketing and good marketing at that because it presents the question, "can it really replace my laptop"?
I think people forget what the ipad was really about when it first was released. In those days there were things called netbooks which were threatening both Apple and Microsofts PC businesses. The big thing about netbooks is that they weren't full computers because they didn't need to be. They were cheap and did a lot of the things users liked pc's for, watch films, email, quick browsing etc.. all slower than a real pc but did the job for a fraction of the cost that real fully featured laptops were going for.
In order for them to be cheap a lot of them used Linux instead of windows, which is why MS were scared. Apple were also a bit worried but refused to make mac netbook because they felt they could not offer the quality that their MacBook range needed and would tarnish their brand. A cheap version off windows just for netbooks and low powered devices was Microsofts answer to the netbook. The ipad was Apple's answer.
The ipad does what netbooks were doing then but in an Apple way and at an Apple price point. They do 80% of what most computer users do, play movies, send emails etc.. that's the whole point of them. They specifically aren't meant to replace fully what a real intel based MacBook Pro would do. Why would Apple sell you a machine that starts at £350 that can do EVERYTHING their £1000 machine can do? They may be into canabilisation but they're not crazy.
At the end of the day, markets are segmented. Apple isn't going to push you in direction of a machine that's half the price of another machine they know you are likely to buy. The ipad is being marketed to people who wouldn't dream of buying a MacBook but would buy a £400 dell because they just need a computer in the house. Those people want to watch Netflix, send emails, maybe edit the odd spreadsheet etc.. and it does all that perfectly. In short they are really going after cheap pc laptop buyers and trying to appeal to them with the idea that they won't lose out on some work stuff if they buy this.
People also miss the point that from a versatility point of view the ipad already surpasses a laptop or pc in different ways. For a start it's more robust, can handle spillage (most laptops are pretty much dead the minute any drink falls on those keys). So you can use them for recipes in kitchens, in the gym, hold them in one hand to read a book whilst standing on the train etc.. Because of their compactness, weight and robustness their usage goes beyond the normal use cases of a laptop anyway. Furthermore, the fact that they are essentially user configurable control services mean they can mimic things that a laptop pc can't. It can be a piano, a dj surface, a games console, a VR device etc..
Right now we have reached the very last aspect of computing that it hasn't (or maybe can't conquer). That of the power user who uses tools like excel and photoshop etc.. where precision selection and shortcuts etc.. are king. Maybe it won't quite do that as well because frankly, the iPads control surface is fundamentally designed differently to mechanical keyboards and mice. However we already have affinity photo so who knows where it will go.
What I will say is that people are forgetting the huge amount of things the ipad arguably does better than a laptop can ever do. This pro workflow issue is like 20% of the game for the target iPad market. I don't think any serious professional in any field would buy a tool that doesn't do what they need it to do. You're not going to buy a a crop sensor camera if you need a full frame are you? That's just all that's going on here. They are both valid options.
