Every season of Discovery has had a finale where it felt like the series could've ended right there.
Season 1 --> Replace the Enterprise scene with the cut scene of Georgiou being recruited into Section 31, and we know where everyone ended up, there's a sense of closure, and the series could stop right there. If the cliffhanger with the Enterprise was amputated, it looked like DSC could've been a one-season series.
Season 2 --> Control is defeated. Discovery jumps into The Future. Pike, Number One, Spock, and Tyler tie up any loose ends. Then it ends with the Enterprise. Spock sees the last signal from Burnham. Pike is ready to take the Enterprise out on its next adventure. You can go straight into SNW. DSC could end right here, leaving The Future an open-ended mystery.
Season 3 --> Discovery proves itself to Future Starfleet, Osyraa's defeated, Saru decides to spend some time on Kaminar, and Burnham's promoted to Captain. If you think of the endgame of Discovery as "Burnham becomes Captain!", the series could stop right there. The original goal has been met. Of course, I'm someone who wanted to actually spend some time with Burnham as Captain, so I'm glad it didn't end there. But it could have.
Season 4 --> Discovery saves the galaxy by successfully communicating with Species 10-C. Tarka is defeated. Starfleet goes easy on Book. Earth has rejoined the Federation, following Ni'Var's lead from earlier in the season. The series could've stopped here.
See the pattern?
So, no, I'm NOT worried that the final episode of Discovery will be another "Turnabout Intruder" or "These Are the Voyages". That's just not what this series is and has never been how it works.
What I'm expcting is that the addendum added will put a button on the series. Nothing more.
Contrast this to ENT where during the first two seasons they acted like it would last seven and meandered, then the third season was a massive "Star Trek Does 9/11" detour, then they only had the fourth season to cram everything in that they wanted to have in. If they'd used the time during the previous seasons more wisely, S4 wouldn't have felt like Cram Season. To the point where TATV had to jump six years ahead to address the formation of the Federation.