Considering that almost all of Donna Troy's appearances in the current continuity were drenched in a grim mood (Meredith Finch & David Finch's "Wonder Woman" run), the fact that Wally's touch opens up memories of Wally and Donna playing a prank together is a refreshing sign. That said, Abnett is clearly playing with the fact that we have two very different histories for the character. In "Titans Hunt," Donna makes reference to her "Wonder Woman" origin as having been recently created by anti-Wonder Woman Amazons, and then later transformed into Fate. Both "Titans Hunt" and now "Titans: Rebirth" #1 are also juggling the idea that she was at one point Wonder Girl, even as this latest flashback also strongly hints that she is still an Amazon.
Nightwing & Tempest
Nightwing and Tempest are the characters whose origins are the most untouched. The glimpses we get of their past involve the friendship between Wally and Dick in taking the Batmobile for a joy ride, while Wally and Garth's flashback has Kid Flash reminding a departing Aqualad that the Titans will always welcome his presence. These scenes help establish Wally as very much a part of the Titans "family," and the glue holding them together. It's apt that Wally's return coincides with the rest of the team finally regaining their memories.
The final page of "Titans Hunt" #8 had the bulk of the original Titans team together, with Herald, Hawk and Dove having flown Bumblebee off to give birth to hers and Herald's baby. There still seems to be room for those four, plus the strangely-not-mentioned Gnarrk, to show up in "Titans" #1 at the end of July.
"Titans: Rebirth" #1 has quickly positioned "Titans" to be a core title for those interested in the mysteries introduced in "DC Universe: Rebirth" #1; perhaps a desire on DC's part to not reveal those secrets too quickly is why the book will only ship once a month unlike most of DC's new twice-monthly titles. "Titans: Rebirth" #1 gives us a love letter to "Teen Titans'" past glories alongside the mystery of how they fit into the new continuity, if at all. This doesn't look to be a mystery being easily solved, but these puzzle pieces promise to intrigue fans.