No real spec here that I’m really going to push, but I am looking forward to read this arc.
The details for
Avengers 57 is
"The Avengers are lost in time, and if they’re going to stop Mephisto’s grand plan, they’ll need help from some of history’s greatest heroes, whose stories have never been told. Like the mystical man of war, Sgt. Szardos, Soldier Supreme of World War II, and his squadron of supernatural grunts, the Secret Invaders…
We may see some new characters but nothing I’d really spec on at the current moment.
Then for all your GHOSTRIDER FANS… we continue with
Avengers 58…
“Japan, the Edo Period. They say he walks by night, wielding a blade forged by hellfire. And where he wanders, the penance flows, like fountains of blood. He is the fabled Ghost Ronin, the Samurai of Vengeance. And alongside the Avengers, he will make his final stand against the lightning swords of the devil himself.”
The cover art for Cover A on that one looks solid to me.
I’m pretty sure this Avenger run is going to lead us in to
AVENGERS 1000000 BC #1
which is also being done by Jason Aaron. A lot of those first appearances were in Marvel Legacy.
I picked up multiple of those origin stories several years ago
Ghostrider - Avengers 7 (Vol. 8) [Them 2nd Prints on that one too…] 
Iron Fist - Avengers 13 (Vol. 8)
Starbrand (Vnn) [Look Like Hulk] - Avengers 26 (vol. 8)
Phoenix (Firehair) Avengers 39 (vol. 8)