Here are some additional factors that may possibly affect the market share:
Apple makes good products and we're sure they are not diminishing. Because Apple controls both the hardware and software (iOS), it has a distinct advantage over Android which is used on multiple types of hardware platforms. Unlike the personal computing market, many users never re-install their phones operating system so it is up to each device handset manufacturer to ensure that Android runs well on their hardware. On a personal note, the Galaxy III S is one lean, mean beast of a phone and is my favorite.
2. Ease of Programming
3. Developer Tooling
XCode is used by iOS developer while Android developers are free to use whatever they want. Since xCode's inception, it has steadily improved. Eclipse is commonly used by Android developers and has some challenges (R.java anyone???). Intellij's new IDEA is very promising for Android development. I currently develop on Intellij 11 and may try out 12 with some new Android features and do a series of tutorials on it. There are
Android phones should logically be lower in cost as there is more competition. Having said that, the observations are that price if not as much of a factor given carriers often subsidize this with plans.
Android wins here again hands down. There are simply many different device to choose from rather than sticking to the iPhone.
There are more factors beyond this however the summary is clear. Android is here to stay and will remain a dominent force in the marketplace.