With a trade war, it could be much sooner, and much worse. A normal recession would see inflation followed by consumer retraction and then a recession. A trade war would be higher consumer prices plus immediate job losses. We'd have spiraling prices and large job losses, similar to the stagflation of the 1970s.

Without the trade war, the yield curve is pointing to Spring 2020 as the next downturn.

http://www.investmentnews.com/article/20180607/FREE/180609925/yield-curve-points-to-recession-in-about-22-months