The WrestleMania card is starting to take shape but, as of right now, there are no plans for The Undertaker.
Last year, he competed in a brief match with John Cena but after a busy 2018, it sounds like the Deadman is taking a break. The last time we saw him, he was on the losing end of a tag team match which saw him team up with Kane to take on Triple H and Shawn Michaels at Crown Jewel.
It's strange that WWE has no plans for The Undertaker but it makes sense in some ways as there are no obvious opponents for him right now and he could probably do with some time to rest up.
The Undertaker is, of course, synonymous with the Showcase of the Immortals but he could always compete next year. We'll just have to wait and see how things play out but Cena also doesn't have a match, so we'll presumably see more matches added in the coming weeks.