Flank McLargehuge posts at the New Warriors Message Board that Darkhawk has a quick one-panel appearance in a flashback in Beyond! #3.
Spoilers after the jump.
Flank writes that Darkhawk “was kidnapped with a number of other heroes by the Beyonder at some point, and forced to fight on Battleworld. Afterward, he was sent home with no memories of the situation.”
“Of course, as revealed in this issue, things aren’t what they seem on Battleworld, so this may be faulty information…”
For now, I’m going to assume that the information Deathlok relays to the other characters through the flashback is accurate. Going by Deathlok’s last appearances according to the Marvel Chronology Project, and the fact that Darkhawk is depicted in his original armor, I’ve placed this appearance right before Avengers volume 3 #1. Maybe something happened on Battleworld that caused Darkhawk’s change back to his original armor. This may change as new information becomes available.