Way back in the day, one of the biggest criticisms of Voyager was the use of the so-called "reset button." Basically due to pressure from the studio, the show studiously avoided any sense of serialization greater than a two-part episode. Unless the writers eventually decided that a given show would have a "sequel" it was unlikely the events would ever be mentioned again. Thus the ship could go from trashed in one episode to brand-spanking new in the next. Or Neelix could have an existential crisis around death, Torres could be "born again" or Janeway could have salamander babies with Tom Paris and no one ever remarked upon it again. The stakes for the series as a whole were thus lowered, because we knew that no matter what happened onscreen, it didn't really matter in the longer run - it was just there to entertain us for 40-some odd minutes.
I would propose that with the season finale, the reset button has been effectively dusted off for Discovery. I am sure that there will be some callbacks to the first two seasons here and there, but not all that many more than Voyager had from episode to episode.
The last act of the season finale pretty definitively closed out every single arc in seasons one and two, provided Discovery does not eventually return to the 23rd century.
I would propose that with the season finale, the reset button has been effectively dusted off for Discovery. I am sure that there will be some callbacks to the first two seasons here and there, but not all that many more than Voyager had from episode to episode.
The last act of the season finale pretty definitively closed out every single arc in seasons one and two, provided Discovery does not eventually return to the 23rd century.
- Control is dead as a doornail. Not completely clear based upon what happened onscreen, but Kurtzman has confirmed.
- Everything related to Discovery, the Spore Drive, and Michael Burnham has been classified. Of course they still had a within-universe impact, but in terms of the "internal lore" of Trek history, they are supposed to have been totally forgotten.
- We are likely never seeing Ash Tyler, Pike, Spock, Amanda, Sarek, L'Rell, Siranna, or Mudd on the show again (even if we see them elsewhere). Oh, and Cornwell and Leland are dead. It's pretty unlikely that PU Lorca will ever raise his head either come to think of it. Basically half of the established character relationships are totally
- Michael has the most obvious existing hook, as her birth mother should be in the time frame in question, and they should be reunited. However, basically every other element of her backstory has been rendered largely irrelevant by the time jump. It can still inform who she is as a character now, but unless they really want to go down the excessive flashback route, her relationships with Spock, Amanda, Sarek, etc just won't have any relevance in the next season.
- Saru's character growth in terms of his "evolution" (in a pokemon sense) remains in force. However, the personal link to his sister is gone. Unless we rediscover his people in the far future, there doesn't seem like any existing personal hook that can be investigated here.
- It was nice (though a bit forced) to see Stamets and Culber reunited at the end of the last episode. However, in a lot of ways their relationship has just been re-established at the point it should have been to begin with - a healthy, functional one which happens to be the first same-sex couple in Trek history. I don't think belaboring the drama they had in the second season too heavily into the third would work well from a story perspective, meaning a "reboot" of their relationship to some extent seems likely. Beyond that, I guess they could do more with Stamets being the "spore guy" - though honestly figuring out how to be something else besides that might be the more compelling story.
- A number of characters have only been fleshed out in a cursory manner, to the degree that what happened in the first two seasons barely seems to matter. This includes Tilly as a main character, recurring characters like Reno, and the bridge furniture (even though they got a bit more of a place in the sun this season).
- Oh, and of course there is MU Georgiou. Her unique backstory is what helps to define her...erm...perspective on things. However, even in the second season, there were relatively few callbacks to her actions in the first. She doesn't appear to have any notable dangling plot threads (other than her continued feelings for Burnham) and we know that she is off the show after the third season, even if the show continues on past her, meaning she has an expiration date.