Silence doesn't mean that it has to be something bad, there is such a thing as companionable silence. I mean, not every good friendship has to talk all the time for it to be good. One of my best friends and I hang out together all the time, we carpool together to and from school, and we go see movies all the time, but we don't feel the need to speak to each other every single moment. Sometimes we just stand in some place or sit some place and be silent in our own thoughts. It doesn't mean that there is tension or that we don't like each other.
And it wouldn't be the first time that there is silence on a filming set, it could be that the next scene is up quick so neither of them have time to go goof around, we don't know the full situation. And besides, since they are filming the finale, they're probably more serious than usual with the final episode in hopes of it being the best. I mean, there are many times serious work to be done, so both Jon and Adam are probably focused at that moment so that they didn't get a chance to joke around. There is a time for joking and playing games and a time to get serious and get down to work. This is probably one of them considering that it is the season finale. And it looked like toward the end that Jon and Adam are discussing and gesturing about something to each other and to that unknown actor.
I don't see any tension with the crew or the actors, they seem like they are simply hard at work and focus with their jobs.
I am excited for that finale, and I sure hope that if Miami is going with the whole "CSIs dropping like flies" type of stunt that NY pulled last season finale with that shootout at the bar, Miami better come up with a better season premiere than NY did. Because quite frankly, NY had been my favorite CSI show right up until I was so disappointed by their season premiere and that six months later storyline that the rest of the season didn't intrigue me and I jumped ship to Miami. Here is me hoping that Miami will deal with the CSIs-in-jeopardy storyline better instead of white-washing it into just another regular crime of the week drama.
I wouldn't want any of the cast to leave, and it's not the first show to carry a large ensemble cast either, they can make it work rotating cast members. They have 8 series regulars(David, Emily, Adam, Jon, Rex, Eva, Omar, and Eddie Cibrian) with one recurring ME character while NY also has 8 series regulars(Gary, Melina, Carmine, Anna, Harper, Robert, AJ, and Eddie Cahill)as well. So if NY has been able to work with that for over two seasons, I see no reason why Miami can't do the same. They can split and do multiple cases like NY used to do a lot over the years.
As for the finale, I'm hoping to see that the episode ends with just all the CSIs lying unconscious on the floor or something, maybe a camera shot of each of the main stars. One of the things that always got me when Horatio was "shot" in the season 6 finale was that while I knew he wasn't dead 'cause they wouldn't get rid of David Caruso, it still jarred me A LOT to see Horatio lying there on the ground trying to breath because he is normally such a stoic and almost invincible seeming and superman-like character, the man you can always count on to get the bad guys and be the strong foundation of the team, that when you see him fall to the ground, it's almost a surreal moment where you couldn't believe that it's happening, that it's the first time you saw Horatio fall and be hurt just like a normal person. So I hope this finale offers some of that jarring feeling!