Claudia Black's been filming two TV series this year which would leave no time for Uncharted 4.
That does not have to be an issue. P-cap is incredibly fast compared to TV productions, there's very little setup time for takes (a few minutes at most, unless the scene involves stunts - but those are usually not performed by actors), there's no need for make-up and hair or complex wardrobe, and so on - so you can record a LOT of material in just a few days. Secondary characters usually only appear in a fraction of the story cinematics, and their ingame animations are usually not unique so you don't need the talent for that. Oh and it's not uncommon to push 10+ hour days when necessary, either.
I'd say that it's quite possible for any TV actor to set aside a few days for such a role. I'm sure they get days off on TV shows, especially if they're not the leads, and that should be enough for all the p-cap that a secondary character could require. If anything can be tricky here, it's scenes where multiple secondary characters should be present at once, because then the availability of multiple actors has to be matched (the leads are usually contracted in a way that it's not a problem with them). But even then, you can always record some scenes with a stand-in and then re-shoot the part for the missing person later, as seen in the Halo 5 intro with Nathan Fillion, for example.
Edit:
For reference, I think our usual time for p-cap on 2-4 minute long trailers or individual cinematics is something like 3-5 days, which includes rehearsal, coreography, and pick-ups as well. And it's not uncommon to do 10+ takes for action scenes and such.
If anyone's interested, I can probably look up the actual times for the Round Table cinematic in Destiny: The Taken King that we did this summer. Hopefully it's not considered to be NDA worthy information
Another advantage of p-cap over live action is that you can shoot the entire scene at once, you don't have to split it up into separate takes by shot and you can do the cuts later. You can also cut and paste performances from separate takes together and hide the changes in the edit, or have the animators fix the transitions manually. So it's incredibly flexible and fast and efficient.