[spoiler]Just a thought about at what point the Supergirl crossover takes place in the Flash timeline. That device Barry was wearing in the crossover, I knew it looked familiar because it looked like the device Thawne used to boost his speed in the first season. It makes sense after last night's episode. So would that mean Barry's trip to Supergirl's Earth may have happened when they tried to test it?
It would be funny to see Cisco's reaction to Barry's trip, and make references to an alien blonde.
[/spoiler]
Also, perhaps it is irony considering the prominent roles the Barry Allen Flash and Supergirl played in the original
Crisis on Infinite Earths. Hopefully they will not be martyrs.