Data from App Annie suggests that global mobile app revenue will hit $50B this year, and $101B by 2020. Total annual downloads will rise from 111B last year to 284B by 2020.

Apple’s iOS is set to retain its store leadership by gross revenue over the five-year period, while Google Play and third-party Android stores will expand their lead measured in downloads due to wider proliferation of devices.

The forecast was made a month after Apple announced a new record for App Store sales, hitting over $1.1B revenue in just two weeks of the holiday season.

App Annie suggests that China will overtake the U.S. in app revenue in the first half of this year, and cites good evidence for this …

China already overtook the U.S. in downloads early last year, but lower average prices mean that it will take a little while longer for revenue to catch up.

The firm predicts that the total number of smartphones and tablets on the planet will hit 6.2 billion by 2020 – up from 2.6B today. The analytics company told Bloomberg that the strongest growth will be seen in India, Indonesia, China, Mexico, Brazil and Turkey as cheaper phones hit the market.

For many of those in developing countries, the post-PC era has already arrived, a smartphone or tablet serving as their only Internet-enabled device.