I recently purchased and downloaded Destiny 2 and the witch queen DLC for my Xbox series x but I have primarily played Destiny 2 on PS4 up to the forsaken DLC. If I enable cross play with my PS4 characters as my primary characters will I be able to play the witch queen DLC that I have purchased for xbox?
If you mean set up cross play on your current PS4 account and new Xbox account, then play your PS4 characters on your Xbox, yes you can.
You just can't play WQ content on your PS4 as dlcs are locked to platforms.
Setting up crossplay is easy just BE SURE TO CHOOSE THE PS4 CHARACTERS as your selected characters. Add your Xbox acc, then you can login on your Xbox n use your PS4 characters :)