Today quite a few apps work offline; there's even a section in the Chrome Web Store that makes them easy to find. This improvement, coupled with the fact that like PCs and Macs users are rarely offline, make Chrome work like most platforms. Google isn't content with this, and recently mandated that legacy packaged apps must go away by the end of the year, and will get kicked out of the store.
But it won't help that chromebooks is way too limited anyways. Why? Because there is not enough Apps available and I can't see that change anytime soon. Not many professional developers will develop for chrome OS where they hardly can get any revenue. They will still stay with iOS and develop professional Apps for the iPad and iPhone.
There is almost only Google Apps available. Most of the other Apps is just “hobby” developed. Quite amateurish Apps. Yes there is a few good Apps, but not many that is as good as real native Apps for real computers or the iPad.
As long as the chrome OS Eco system is as terrible as it is, the iPad will be a much better buy. It's not so limited as a chromebook is.
So I highly recommend buying the iPad Air instead. It can replace a computer for real.