I don't think Bronn or Jamie are dead. They would've showed Bronn if he died so he's definitely alive. Jamie is a little trickier. It did look like he was sinking with his heavy armor on. But if they really wanted to kill off a major character like that, they would've given him a better finish, like having Drogon fire blast him. I think he'll probably get out of the water and end up being captured by Daenerys. It would be interesting to see Tyrion become reunited with his former best friend Bronn and his brother Jamie. And it'll keep the idea alive that Jamie will be the one to kill Cersei. Having him just plunge down into the water like that would be the most anticlimactic death ever on the show by far.