Fear the Walking Dead jumped far into its narrative's future for Season 4, which left a lot of Season 3's remaining plot strands left dangling. Daniel Salazar was definitely one of those strands, with the fate of Rubén Blades' dangerous badass left up in the air. We do know he'll return in the future in some capacity, and it looks like the midseason finale may have foreshadowed his eventual return, although it's unclear where in the timeline Daniel's return might happen.
Fear the Walking Dead didn't make any grand gestures hinting at Daniel's return, because that would be too easy. Instead, fans had to look quick to catch a particular set of initials marked on one of Althea's video labels. See the bottom tape in the second column. (Which is actually the top tape of the second column when viewed right-side-up, as it was shown in the episode.)
While the letters "D.S." could technically stand for a plethora of different things that have nothing to do with fan-favorite characters from previous seasons, it almost feels a little too on the nose to stand for anything but "Daniel Salazar," especially considering the fact that Al's videos also included a reference to Abraham and Eugene having been subjected to her interview process when they were still in Texas. Sure, Al could have interviewed actor Dan Stevens, former baseball great Daryl Strawberry, author Danielle Steele, etc. But we know that the Fear the Walking Dead creative team looks for ways to create connective tissue like this when applicable, so D.S. should only mean one thing.
If Al did catch up with Daniel to trade him something for his story, I can only imagine how shaken she was whenever he finished, assuming he didn't hold back on the facts. His dark past from before the outbreak didn't exactly begin to shine any brighter as he lost his family members and spent huge chunks of time away from the main narrative. But will his return be in the most current storyline, or will we only get to witness his interview via video? Since we have no idea how he survived the events at the dam in the Season 3 finale, it's hard to tell how hard traveling through Texas would have been for him.
The quick shot of Al's tapes in the first chunk of the episode definitely wasn't Fear the Walking Dead's most important midseason finale moment. That would have been the final act, when it was finally revealed that Madison did indeed sacrifice herself in order to secure safety for Nick and Alicia. (Though we have some issues with that outcome.) But as terrible as Madison's death was, it seemed to definitively close out Season 4's first chapter, which could possibly allow for the second half of the season to re-introduce Daniel Salazar into the storyline. I think he and Morgan would get along fancily.