OnePlus might come up with new branding for Dash Charge as it's been recently discovered that it lacks the trademark in the EU after both Amazon and Bragi have filed against it. This contest against the trademark in Europe and the declined status of it in the region would mean that if it continued to use the Dash Charge name in the U.S. where it does own the trademark but not in Europe, then it would have split-branding which is likely not what the company wants for its products.
While it's not clear just yet what OnePlus would use for a new brand name for Dash Charge it does seem like it has already started taking the necessary steps to shift the name of its proprietary charging technology. During the OnePlus 6 announcement event the company never once referred to the charging as Dash Charge, instead calling it fast charging technology. It's also been reported that the company is no longer using the Dash Charge name anywhere on the website or in its product listings on the web store for products that have had the Dash Charging technology.
OnePlus phones from the OnePlus 3 onward also used to say "Dash Charging" when the phone was plugged in, but now with the latest beta software the devices are reported to say "charging rapidly" instead. OnePlus has very subtly began moving away from using Dash Charge anywhere, and although it hasn't been trying to actively hide this change it also hasn't yet publicly mentioned anything about the change or an official decision to shift the branding to a new label. It's possible that OnePlus is already working on coming up with a new brand name for Dash Charge but it's just as possible that it could simply stick with referring to it as Fast Charging, while having the phone say charging rapidly when it's actually on the charger.