I mean they are still not confirmed like 2019. releases so technically they can't be pushed back to 2020. All depends when those games will be finished, if one of them is finished and ready for 2019. launch, I dont think Nintendo would push them in 2020.
I am not so sure. I think they had Yoshi title almost ready for 2018, and it was pushed back to 2019 due to marketing / calendar. The same happens with New Super Mario Bros Deluxe of course, which could have been out in 2018 but they have set the release window for January 2019 to keep Switch moment from Christmas and Smash in the beginning of 2019