That depends. If the ships are alien, and those aliens have no connection to the Federation, then those aliens might just as easily have weapons that are less advanced as they are likely to have weapons that are more advanced. But that's the same as it is for TOS, TNG, DS9, VOY, or ENT. If (for example) Picard met a previously unknown alien species from outside the Federation, there is no reason why that alien's weapons would be at the same level as the Enterprise's weapons. Or Voyager running into a Delta Quadrant species. And that's assuming that if they do go into the future -- say the 32nd or 33rd century -- there is still a Federation. If they go to a future where the Federation as we know it has collapsed or changed (which is hinted at in the short trek Calypso), then maybe some Federation technology has been lost to time, and the Discovery's weapons are a good -- or better -- match for the types of weapons they might encounter. Or they upgrade once they get there.