OK, so I just had a brain storm. Power Hank Pym's quantum realm entry thingy with the reality stone which Clint somehow steals (red glow, first trailer) and infiltrate (cool uniforms during the Hero Walk) reality from a different quantum point, fly through a whole lot of bits of past and alternate reality (Steve back in the recruitment poster, Clint and Cute Girl And Bow) and .... presto.

Second brainstorm. That scene with Clint and Nat? So the Restoration didn't QUITE work and he lost his family in that process (wait. what? I've written a fic about that idea ... :P) and what we see is the mid-credit scene where she comes and brings him home. Ouch.

But wait... we have hair that goes from short blond to longer blond to red with dipped tips. What if there's no time TRAVEL but simply the passage of time? What if things take place over YEARS? What if Clint does lose his family but in the years after he grows closer to Natasha in ways he hadn't been before?

(I'm a hopeless romantic and since I'm stuck with Whedon's mess, I'm trying to make the most of it. I don't want to discount the entire family.)

That's my read, as well and also the theory I was talking about in a different thread somewhere... the red -> white isn't a "style" so much as "they've been on the run for YEARS and there's no time for a dye or haircut" and thus the movie takes place over several years :o