"Smartphone application processors (AP) worldwide will grow 1.5% to 1.67 billion units in 2018," DIgitimes estimates. Consensus is smartphone sales in 2018 will be about flat. Since accuracy for forecasts like this is +- several percent, don't make too much of the exact estimate. Some China Q1 sales are low enough to suggest a decrease in 2018. Digitimes has become a reliable source which I regularly check.
What's interesting here is the market shares. As smaller phone vendors fall out, the share of Samsung, Apple, and Huawei HiSilicon self-produced chips rises. They are usually the three biggest vendors and predominate in the more profitable high end chips. Company after company have failed in the wireless chip business.