Usually it's better to stay within a system so it's not a bad choice. However, it depends on how much the lens are as well. If it's super cheap, you might not lose much to switch if you consider it.
Assuming you do a lot of sport, a D500 will do very well since it's AF is similar to the D5. Landscape and portraits would benefit more from higher MP, like the d850 but 24MP isn't bad. If you don't need more than 24MP, than it would be a good setup.
I believe the D500 is the best AF on a crop body unless the 7dII or a6900 comes out.
One thing to add is that one card slot is SD and the other one is XQD I believe so do be mindful to get a card for that other slot since it has faster writeout which matters for sport.