There are several explanations here, it could mean the Zen 2-based Threadripper got cancelled or got delayed to 2020. Alternatively, it could be that we're reading too much into this and that the chip is still slated for 2019.
Guess we'll learn more in the coming weeks and months.
AMD Investor Presentation May 2019
— 188? (@momomo_us) May 3, 2019
3rd Gen Ryzen : MID-YEAR
3rd Gen Ryzen TR : delete
Zen 3 : On Track
Zen 4 : In Design
EPYC Rome : Expected Q3 2019 pic.twitter.com/0xF8Ghcn6P