There are reports and there are reports. From the latter category, we are being enlightened with the latest growth predictions for Android and they come out at a whopping 900% for 2009, compared to "only" 79% for the iPhone. The report does not hide the fact that the calculatory basis may not be fully comparable as it is expanding from a low base.
Moreover though, when looking at the models applied by Apple and the Google-led Open Handset Alliance, these are quite different and it is therefore to be fully expected that Android-powered handsets will overtake iPhone numbers sooner rather than later. Would they not, it would simply reflect on extremely poor performance: Apple has always applied a model that combined hardware and OS: both came from the same mould and from one hand. This is a huge contributor to its superior usability: it can be woven in a seamless way.
However, on the other hand, this is also what arguably cost Apple the war over the desktop: Microsoft-powered systems grew exponentially, last but not least because the OS was available on hardware from any number of manufacturers whereas Apple's OS was only available on, well, Macs. The same applies now to the iPhone. Apple's one product that bucked that trend was the iPod, which commands an impressive share around 70%. This however is the exception rather than the norm. And it is unsurprising, too: it is extremely unlikely that one manufacturer and the limited number of models it can bring out will be able to cater to the needs and tastes of any number of people and demands equally.
The above does of course not mean that Apple did much wrong: the model seems to be working beautifully. The app store might only have contributed $20-45m or so in profit (or revenue?) to Apple (which is not that much considering that this is the harvest from more than 1 bn apps) but it also sold 13.7m iPhones and 22.7m iPods in 2008 alone, and this will have contributed nicely. Now, take this together with the Mac boom (which still only equates to c. 10% market share), which arguably is partly to "blame" on the popularity of iPhones and iPods (many users will experience the legendary UI only on one of these devices), and you have a good company.
The Android model is the opposite of this: here, a large number of companies get together to build an OS, which can then go (and be customized) on a myriad of devices from a myriad of manufacturers. At the start of the initiative, it was Google and 34 others, including China Mobile, KDDI, Sprint, TIM, T-Mobile, Motorola, Samsung, HTC, Intel and eBay (cf. here). Today, the alliance boasts (if I counted correctly) 47 members. As per the above equation, it would be very surprising if the numbers from this model would not exceed the ones from Apple's. In 2009, we will be seeing Android devices from HTC (the front runners on this with the G1 and the Magic) as well as from Samsung, LG, Sony Ericsson and probably dozens more. Can they sell more? Yes. Will they sell more Android devices than iPhones in 2009? I don't know. Maybe not. Will they still grow by 900%? Yes, of course, as we are still looking at small numbers at this time: if I make $100 turnover in year 1 and $900 in year 2, I still cannot live of that but I will have grown 900%... Will they be able to grow by 900% in 2010? That will be more difficult as their starting point will be different. Very wise insights, huh? ;-)