To me, it depends.
If D&D goes back to where a few challenges and monsters are magic item dependent, there definitely needs to be a few in the PHB so players know they might need a few.
Things like oathbows and holy avengers that are tied to races and classes should be included in the race and class chapter for flavor.
Potions and other very minor magic items like holy waters and alchemist fire should be in the equipment chapter.
But everything else in the DMG.
If D&D goes back to where a few challenges and monsters are magic item dependent, there definitely needs to be a few in the PHB so players know they might need a few.
Things like oathbows and holy avengers that are tied to races and classes should be included in the race and class chapter for flavor.
Potions and other very minor magic items like holy waters and alchemist fire should be in the equipment chapter.
But everything else in the DMG.