Blizzard Clarifies How Loot Boxes and Currency Will Transfer To Overwatch 2 - IGN - IGN
However, for anyone still keeping their loot boxes, those will be opened automatically and their contents will be transferred to your account in the sequel.
"We'll share a more detailed explanation on all of these topics before Overwatch 2 goes live in October.To give you a quick answer now though, those existing currencies (credits, OWL tokens, and competitive points) will come with you into Overwatch 2," writes Overwatch commercial lead Jon Spector.