How the movie could end

It ends kinda ambiguous but I'd say yes on the new reset universe, he ran into what he thought was the regular DC universe that we have seen in a couple of movies now but he didn't go back without changing anything, when Bruce Wayne came up with his car and got out Barry was surprised about who it was and we never got to see. Before the movie the director talked some and that the movie wasn't 100% complete yet and might be subject to change

I saw this in a reddit post, so I could support this claim, James Gunn even said that he is open to keeping Miller (depending on his recovery) and other actors like Gal Gadot and Jason Momoa.

Apparently the movie had several endings shot, one where Barry returns to the main DCEU timeline where Keaton is the main Batman (replacing Batfleck) and there was reshoots in September with a supposedly a new ending filmed with Batfleck, with appearances from other DCEU actors, like Henry Cavill and Gadot, but these changed when MoS2 and Wonder Woman 3 were scrapped and now we'll have new actors playing Batman and Superman.

The Flash looks like it could be a good movie so I can't wait to see it