In March of last year, business information specialist, Informa predicted that Android would outsell iPhone by 2012.  Depending who you ask, that may have happened already, two years early.

With that in mind, Informa this week predicts that Android will pass Nokia (NOK) to become the biggest smartphone platform on earth in 2012.  And Android won’t stop growing there.  Informa expects the Android platform to top half a billion handsets in use by 2015.

Nokia will lose out most from the trend, according to principal analyst Malik Kamal-Saadi. “Informa expects that the market share of Symbian, from total smartphone users, to drop significantly from 53 per cent in 2009 to 32 per cent in 2015. In terms of sales, smartphones powered by Android are expected to surpass these of Symbian as early as 2012,” he said.

Google (GOOG) says they are activating 200,000 Android phones/day currently.  At that run rate, over a given average two year life expectancy of a phone, Google is currently on pace to have 147 million Android devices in circulation — if sales are flat.

That means that Google hast to grow by just over 3x in the next four years if they want to meet the half billion milestone.

Luckily for Google, sales are anything but flat.

Another wildcard: If Nokia doesn’t see a rebound next year, Kamal-Saadi predicts the temptation to at least partially embrace Android will prove too strong.  If Nokia goes Android, he expects Android to enjoy a Windows-type monopoly over the smartphone market.

For what it is worth, soon to be ex- Nokia VP Anssi Vanjoki compared the strategy of going to Android to young boys peeing in their pants for warmth or being short lived.

To give an idea of scale, Informa also predicts that the smartphone market will pass the 1 billion handset milestone in 2013.  Google CEO Eric Schmidt mentioned last month that he thinks of Android as a money maker that scales massively along these lines.

“If we have a billion people using Android, you think we can’t make money from that?” Schmidt asked rhetorically. All it would take, he said, is $10 per user per year.