They came in 2016. In 2017 and 2018 we only had to play one NFC West team each year; 2017 was a road game to Los Angeles since we both finished 3rd in our divisions in 2016 and in 2018 they came here after we both won our divisions last year.
The next time they’re guaranteed to come here is 2022 but they may have to come here in 2020, 2024, and 2026 depending on where both teams finish the year prior.