Depends. Tit for tat doesn’t have to escalate that far if tits and tats are relatively equivalent to each other, but someone has has to be the one to stop at some point or the escalation will grow.
Problem we have is, if we let Assad (and Russia obviously at this point, or they would be so hardline on it) get away with using chemical weapons without a response, it will happen again and/or more frequently
Why do we let our rebels get away with chemical weapons use?
Perhaps Russia will sink a ship. At that point, Americans have a choice. Stay out if Syria or escalate the war.
I figure Trump won’t do much if Russia stinks one of our ships.