He's just saying there is little room for innovation in the tablet hardware space. I'd tend to agree. Once all tablets are light, responsive, high resolution, reasonably powered (RAM/CPU), and have all the standard frills you're really past the point of diminishing returns IMHO. There's not much you can do with an iPad 3 you could't do with the first iPad, though it's a nicer experience. The iPad 6 is probably going to be much less of a leap from the iPad 3 than the 3 was from the original.
And again, that's 20/20 hindsight. Go look at the tablets that were on sale in 2009. Do you think that the innovation fairy just started shooting Skittles out that magically gave the iPad a huge leap? Innovation isn't always in engineering terms, boosting cycles etc. Sometimes it's in reimagining how things can be done.
Even a technology considered relatively mature (cars) changes a lot, in subtle yet important details.
Just because you can't foresee change in existing markets doesn't mean it won't occur.
