Toyota is correct and the US auto market has peaked, meaning that total sales by all industry participants combined will barely budge in 2017, then market share is the name of the game. The only way for one company or brand to show growth is by taking share away from a different company or brand (including cannibalizing a brand in the parent's portfolio).
This situation will have a major influence on automaker's US marketing plans for the coming 18-24 months. So far, the signs point to a plateau.
For starters, consumers will likely benefit from increased financial incentives (rebates, for instance) as dealers and brands court switchers or try to hold onto usually brand-loyal customers. Dealers are also benefiting from manufacturers' financial incentives, which they may or may not pass along to consumers in the form of reduced effective pricing.
A table on the Wall Street Journal site shows that sales of light trucks are picking up speed vs sales of passenger cars. Gas prices are low, so even though SUVs and pickups don't deliver fuel efficiency equivalent to cars, buyers are returning to their truck-buying habits.
As a result, the market share brawl is not just a matter of, say, GM vs Toyota, but also cars vs SUVs and pickups, plus gas vs hybrids vs electric. How to stand out? For example, for differentiation and to appeal to targeted segments, Volvo is going all electric by 2019. What complicates this brawl is the aggressive entry of Tesla and its popularly-priced electric car (image at top). The market share brawl is underway!