I did a quick Google search to answer my question about information sources and this is what I found. And I have to say… this is the most promising thing I have seen or heard regarding Loki’s fate in IW/A4. Tony going back in time to spring Loki from captivity in The Avengers? I would definitely be here for that.

I also found this story about reports that Aaron Taylor-Johnson, who plays Pietro Maximoff, had been seen on the set of Avengers 4.

What I’m not sure about is whether this has any consequences for their future survival past the point when, in the original timeline, they died. Whoever is doing the time travel shenanigans might be operating according to some kind of “least disturbance” principle – retrieving the Infinity Stones so that Thanos can’t get them, but otherwise leaving things the way they were.

This also doesn’t necessarily mean that Loki will have a significant role in A4, and based on some of the obnoxious things the Russos have said, I still don’t have a lot of hope that he will. He might just have a couple of cameos from the past while our heroes work around him to get/destroy the Infinity Stones; I’m still not at all confident that the writers or directors care enough about giving Loki a satisfying narrative arc to give him any agency in the effort to defeat Thanos, despite the fact that he clearly has some previous experience with Thanos and personal reasons to want to take him down. And I will still be pretty pissed if he’s basically just background scenery for other people’s heroics and if his IW death is still the end of his story.

‘Avengers 4’ Set Photos Reveal Major Plot Point That Could Change Everything