A few points.
Yes, for those whose "computing" needs consist solely of (limited) content consumption coupled with basic communication, the iPad is a great device. In fact, such folks have been forced to "overbuy" for some years.
(As an aside, it's ironic that when Microsoft "invented" the tablet about a decade ago, it didn't sell because the market for such a basic device didn't yet exist. Apple's greatest coup was recognizing that in the last decade the market has emerged.)
Those who want the iPad to be extended to meet their more extensive computing needs are almost certain to be disappointed. Not only would such extensions complicate life for the market above, the form factor required would almost certainly (at least with today's technology) make the iPad too large and heavy to be the highly portable device it is today.
Which features are you reffering to?
This latter group will be served with new models of ultra-portable PC's that are beginning to emerge. See the Lenovo X220T for a current example and expect the Apple "Air" product line to incorporate more "tablet" features such as a touch screen interface. For those who want a true "laptop replacement," it is that product space that bears watching.
Seems like for my computer needs a MBA with a streaming setup (iCloud or other) is all I need.