While specifics about nearly everything pertaining to Star Trek: Discovery remain cloudy, we do know enough to say that Wesley Crusher and other beloved characters from The Next Generation or Deep Space Nine could easily pop-up on the new show.
The last time we saw Wesley in regular Star Trek canon, he effectively became a Time Lord by joining forces with the soft-spoken interdimensional alien with mitten-hands known as the “Traveler.” Because Discovery will be set about a decade before the original Trek, this puts it about 80-90 years before The Next Generation. Barring time travel or weird flash-forwards, this setting prevents the majority of the Next Generation characters from showing up on Discovery. But, some forms of time travel are not like other time travel, and the Traveler and Wesley can appear all over the place. And, since he’s not a member of Starfleet anymore, Wesley could do all sorts of stuff under pseudonym and not mess with the “regular” flow of time.
An op-ed on Inquisitor recently postulated that the debut of Discovery could pave the way for the very popular cast of the Next Generation to have a “proper send-off” since their final film, Nemesis was so bleak. And while this is a nice thought, it seems specifically unlikely. However, populating the 23rd century of Discovery with occasional visits from 24th century, seems a little more probable, generally. This means a time-traveling Captain Picard is probably not going to happen. But an extra-savvy and possibly centuries-old version of Wesley Crusher? It’s just outlandish enough to make a little sense.
What about other “timeless” Trek beings who could appear on Discovery without altering the timeline? The list is kind of short, but considering Ben Sisko became a being of pure-energy at the end of Deep Space Nine, it’s also not crazy to hope for his appearance in the 23rd century, acting as a prophet to the crew of the Discovery. After Whoopi Goldberg’s comments at a recent Star Trek convention and the ensuing #bringbackguinan campaign, the return of her nearly immortal character to Discovery is also feasible. And though we met Guinan in the 24th century, the TNG episode “Time Arrow” showed us she was alive and sipping cocktails with Mark Twain on 19th century Earth, meaning she traveled around the galaxy enough to potentially hang out with the Discovery people in the 23rd century.
This line of reasoning will lead most hardcore fans of The Next Generation to their ultimate dream: the return of a truly multi-century character totally unbound by the rules of time: the flippant and all-powerful space god, Q! And because he’s basically space-magic, bringing Q to Discovery would be a snap.