I have tried replacing my laptop with an iPad or phablet (and keyboard) and storing files in the cloud. Several times. It seems it should work, but it doesn't for me. Matt Yglesias says most people aren't quite there either.
One problem is that I don't like the iPad software supposed equivalents to my laptop software. E.g., I don't like the "conversation" version of gmail, but that's all that seems available in the gmail app on iPad.
Another problem is that storing and using files from the cloud will take some learning for me.
It will probably happen at some point. Just not yet.