I think the important thing right now is to think of all the possibilities of a fanfic continuation could be. This wasn’t an ending. There’s such a wide opening for what happens next.
So have some of my own headcanons and ideas:
Danny takes time to heal and make sure Lincoln is trained to take over Five-0 and then decides to retire. Maybe Danny moves back to New Jersey with Steve when he comes back? Or Maybe they both stay in Hawaii cause it’s become home for them both.
Danny and Steve talking to each other CONSTANTLY working through time zones and cases to just always be in each other’s lives. Danny tells him what’s going on in everyone’s lives and Steve tells him about his adventures.
Steve comes back after a couple of months of travelling, doing things and going places where he doesn’t need a gun or combat experience. Just relaxing. Maybe he went to Thailand or TIbet and learned meditation techniques for his pts and anxiety. Maybe he went to some of the places he’d been to on a mission but this time he just saw the sights.
Steve sends the team tons of postcards and letters and selfies with monuments. So many, in fact, that they start making a “Where’s McGarrett?” board (ya know, like Where’s Waldo?). It’s huge and full of the stuff he sends home.
When Steve tells them he’s coming home they plan a GIANT welcome home party for him. It’s a surprise party at the McGarrett house and everyone is there. Danny organizes it and gives everyone a mission. Tani is in charge of music, Junior is in charge of decorations, Kamekona handles everything food related, etc.
Danny picks Steve up from the airport and it’s a beautiful reunion full of hugs, smiles, and happy banter.
Or, on a completely different take, maybe Steve comes home a bit early and it’s late at night and he tries to sneak into the house so he doesn’t wake up Danny but Eddie ruins it and starts barking happily at seeing him again. Danny comes out and we get a beautiful McDanno reunion. They spend the night talking (or first half for those who want them to do something else later *wink wink*), Steve regaling Danny with his adventures and Danny telling him what Five-0 has been up to. Steve tells Danny that he and Catherine went to one place together but parted ways as friends soon after when her work called her away.
Maybe Danny tells Steve he wants to retire but he’s not sure what to do now.
Steve tells him he got an offer to become an HPD Academy instructor and he’s gonna take it. Maybe you could see if they got another opening, Danno. Picture Steve teaching advanced combat or something and Danny teaching about detective skills. No danger for either of them but they still have a hand in justice by teaching the next group of cops. They have lunch together everyday and their students love them.
The team threw them both giant retirement parties.
All the things from Danno’s near death vision are coming true. Grace and Will get married at the house, have kids, grandkids.
An option for McRoll and McDanno fans: Steve and Cath actually stay together, get married, and have kids. Now picture Danny helping Steve raise his kids. He babysits all the time, constantly tells worry wart Steve he’s doing great, he’s there for the birth and every big celebration. Just generally being the uncle to Steve’s kids that Steve was to his own kids. Imagine Grace coming home and just gushing over little baby Steve.
Tani and Junior eventually become the captains that Danno visualized in his near death hallucinations and the scene with Charlie entering the academy comes true. They take over the task force when Lou retires.
I have so many thoughts I could explode. Go forth and have fun!