So now that we have all the feels out of the way from "Carry On", the series finale of The CW's Supernatural, let's get to some commentary including some specials and spinoff ideas for the Eric Kripke-created series. So we're throwing on the "MAJOR SPOILERS AHEAD!" sign before we go any further, obviously.
Supernatural "Carry On" Thoughts
For eagle-eyed viewers, the end for the Winchesters was actually foretold cryptically in a previous episode, albeit under much darker circumstances that involved a vampire horde. In the January 16, 2020 episode "The Trap", Chuck (Rob Benedict) informs Sam (Jared Padalecki) one of their many possible grisly fates trying to break him while captured in a casino. He tells Sam that most of the hunters are gone. Claire (Kathryn Newton) dies in a vampire hunt and both Sam and Dean (Jensen Ackles) end up turned into vampires. Jody (Kim Rhodes) and Bobby (Jim Beaver) end up killing both, but not before Dean kills Jody. This wasn't shown on-screen, but since Chuck wrote what the Winchesters do as God, it's hard to really call his bluff. In "Carry On", Sam and Dean have saved the earth from Chuck and allowing Jack (Alexander Calvert) to be the new God, go back to their usual hunting ways. This time their latest case gets them to a vampire brood. As the fight goes down, the final vampire uses his husky frame to shove Dean against a piece of exposed rebar, mortally wounding him before Sam decapitates the vamp from behind. Either way, the Winchesters' journey ended because of vampires.
Spinoff Idea –Claire and Dean. Jr
When it came to Sam living out his natural adult life seemingly "retired" from hunting, we see him raise a child presumably with Eileen (Shoshannah Stern)? That child ends up growing up and sees him off in his final moments. Adult Dean Jr is played by Spencer Borgeson. It might not be a bad idea to have him front the next film and/or series should The CW pull the trigger on it. There's a little bit of a vibe where we could see Padalecki come back when he's not busy with Walker Texas Ranger train him via montages about hunting. Borgeson and Newton can literally front the show together in an aunt-nephew-type relationship where they become the new lead hunters for the spinoff with Claire being the more seasoned of the two, obviously.
Spinoff Idea – Castiel and Crowley
Misha Collins and Mark Sheppard are perfect contrasts to one another as Castiel and Crowley at polar opposites as angel and the once king of hell. With Jack being the new God, it's hard to imagine him simply stepping down. I do see him have a role at times. Before Jack, that the fourth person was Crowley, and before anyone asks why this might make a great series, first, Collins and Sheppard have wonderful chemistry together. Second, this can be the Supernatural version of Good Omens meets Highway to Heaven. I mean seriously, who wouldn't watch the celestial version of The Odd Couple?
Spinoff Idea – John and Mary Winchester and Other Hunter Chronicles
Before Sam and Dean, there was John and Mary and their adventures. Given their ages, it pains me to say that continuity wouldn't allow Jeffrey Dean Morgan and Samantha Smith to simply come back to earth for new adventures. I can see one of them take narrating duties. Obviously, both seen a lot before starting their family. If not recast, a series starring Matt Cohen and Amy Gumenick, who played the younger versions of both characters and their struggles learning the hunt. I can also see the Men of Letters taking a bigger role in the series. The idea doesn't only extend to the Winchester parents, but another pairing that could work is Bobby and Rufus (Steven Williams).
Clearly, the two misfires for spinoffs don't bode well for a franchise future beyond Sam and Dean. If Ackles and Padalecki decide to emerge from the sunset again for some special engagement, just keep it simple. Give the fans a chance to mourn the loss of the series before coming back with their reunion. Given the 15 years of the show, there's plenty of opportunities to cherrypick from the lore to expand again to find their "Space Seed". I doubt you've found a continuation in a form of a theatrical release, but there are plenty of places within the Warner family that feature has with its existing home on The CW, streamer CW Seed, HBO Max, etc. Just do more than a "Best of" compilation.