Where Have You Gone?
This is some speculation about what happened to some supporting
and guest characters after we stopped seeing them on their respective
series.
Saavik
Had
Spock's child from their mating on the Genesis Planet, and then much
later married him (was originally the plan in ST:IV but not shown but
in TNG it's mentioned that Picard attended the wedding of Sarek's son).
Later went on to become a Captain and an Admiral according to some
novels. Thankfully the plans to have the treacherous Vulcan in ST:VI be
Saavik were dropped in favor of creating a new character, Lt. Valeris.
Ben Maxwell
Was
imprisoned, but later released after it turned out his accusations
about the Cardassians were correct. Left Starfleet and became one of
the leading strategists of the Maquis. Survived the Maquis slaughter
and rejoined Starfleet when they needed everyone they could get and
fought on the Cardassian front during the Dominion War.
Thomas Riker
Survived
the destruction on Cardassia by being in an off-world labor camp. After
the war he was released by the new Cardassian government and pursued
Deanna Troi, only to find out she had married Will. Unable to return to
Starfleet because of his repeated actions against it and the fact that
he could still pose as Will Riker, he got a job as a freighter captain.
Sito Jaxa
Instead
of killing her, the Cardassians took her prisoner, tortured her for
information, and told the Federation she died (backing that report up
with debris from her shuttle). They held her for years in the same
labor camp as Riker, and she was finally repatriated after the war. She
has been reinstated in Starfleet with a raise in rank and numerous
medals, but she is also troubled by the years of abuse and torture. She
served on Worf's ambassadorial security detail (at his request) and
later returned with him to the Enterprise-E.
Commander Sela
Was
a hero of the Dominion War where she grudgingly had to ally herself
with Picard and crew. Opposed Shinzon's coup, and took several dozen
Warbird's under her command to a secret location once he launched his
attack on the Romulan Senate. Returned months later after Shinzon was
killed and the USS Titan's task force had left Romulan space (she had
spies observing the whole time), and allied with Commander Donatra to
bring down the government of Praetor Tal'Aura (yes, the same Senator
that planted the Thalaron Bomb in Nemesis) and Proconsul Tomalak (the
new heads of state were named in "Titan: Taking Wing") and established
herself as Praetor with Donatra as Proconsul.
(Theory by Bond, James Bond)