Before this announcement, there were only ever going to be 100 billion dogecoin in existence. Now they just decided that they want a 5 billion doge inflation rate per annum, Thereby decreasing the the value of each dogecoin.
Its somewhat similar to the way that the federal reserve pumps money into the market to increase the flow of capital, the dogecoin foundation wants to increase the flow of dogecoin by increasing the supply and access and decreasing the incentive to hoard.
edit the code was already written to be inflationary. The plan was to implement a 100 billion cap in some future version. They scrapped that plan.