How long before the first malware that infects a billion people?
Maybe it doesn't happen this time, depends on how easy this bug is to find. At any rate there are surely plenty of other bugs lurking in Android that can be remotely triggered in a similar manner. Find one and have it text a random assortment of the infected phone's contacts, and it would spread across the world in a matter of hours. What is done with a billion phone botnet, who knows, but it probably won't be good.
You don't even need Android's famously crappy updating for this. It would spread so fast that if you found a zero day that infected iOS 7 & 8 in a similar manner you'd own 95% of all iPhones in the world even if Apple turned around a patch in 24 hours.
Someday we're going to wake up and know what the Morris Worm would have been like if it had infected five orders of magnitude more devices.
Microsoft ought to immediately start a black project researching for bugs like this in both Android and iOS. Brick a billion phones and a lot of people won't buy the same kind they had before - this may be Microsoft's only hope to get any market share in the mobile market :)