1st, trading down is no guarantee...there has to be a taker
2nd, we pick 8th in the 2nd round, so for the sake of argument, lets say we trade down with a team picking 25th-28th. So, there are potentially 17 teams that could pick a QB (either one of the names you suggest) before we pick.
If we trade down, it is done mainly to accumulate extra picks, not to "wait for a particular player to drop for us."
Aside from maybe the top 10-15 players, all these draft predictions are pure speculation at this time. They will change again after the Combine, and yet again, once the real draft is under way. There will be LOTS of surprise picks.