In fairness, the question is less "how many vulns does this exact device have so far" and more "how many vulns are likely to occur for this device total", in which case this article could be evidence that the last few versions of iOS have each had their share, and therefore it is reasonable to extrapolate that to expect a handful of issues on this version. Now the first obvious catch is that you can't necessarily accurately project the past into the future; if most of these are the result of some underlying design strategy that Apple has stopped doing, then the exploits would dry up. On the other hand, of course, they could start shipping some new technology that turns out to introduce more vulns (not likely, but it could happen).

Of course, I'm pretty sure the same list of exploits per-version of Android would be much longer, so if anything this list, if complete, really does paint iOS in a very good light.