I know how the new training system works as a single queue and the calculation of training time. What I am wondering is say I have all level 6 barracks and the wizards are being trained for say n seconds, if I upgrade one barrack, will it increase the training time of say wizard or any other troop in that case until the barrack is being upgraded or will the training time be the same throughout.
Yes. Just as before the update, upgrading a barrack will increase the training time of your troops.
Here's an example (wizards) of their training time depending on the number of barracks available :
1 lvl 6 barrack: 2 min training time
2 lvl 6 barracks: 1 min training time
3 lvl 6 barracks: 40 sec training time
4 lvl 6 barracks: 30 sec training time
Note that the training time does not depend on the level of the barrack.
3 lvl 6 barracks + 1 upgrading barracks = 3 available barracks = 40sec training time.
Here's the proof on my own village :