In one continuity, the Bad Batch exists, he returns as a cyborg and he joins their team. better than ever. But in another....they don't exist and Echo unfortunately stays dead, although George Lucas wanted to put them in those TCW concepts when the show was cancelled.
In Legends, Fives joins Echo in valhalla. But in Canon, Fives dies first and Echo is destined to join Fives soon...
Wow, what a coincidence. This was my 1409th post and I didn't expect it to be about Echo in the slightest!