https://www.pcgamer.com/metro-exodus-delayed-to-2019/

Metro Exodus is bigger than 2033 and Last Light combined, making it the most ambitious entry of the survival shooter series yet. Announced at E3 2017, we'd hoped to endure its barren landscapes and irradiated mutants this year—but publisher Deep Silver has now announced it's slipped to 2019. 

"The development of Metro Exodus is progressing well; we are all really excited by what we are seeing," says Deep Silver in a statement. "We have been constantly reviewing the games progress to ensure that we deliver a product that gamers and fans of the Metro series want and deserve, as well as keeping an eye on announcements from our competitor products.