However, you can trade up your multiclass powers for another (higher/current level) multiclass power at every single level.
This is incorrect if you are talking about the power swap feats. Whatever power from your original class that you traded to get a multiclass power is the max level of the new power you can gain. For example if you swap a level 1 encounter power from your original class you can ONLY get a level 1 encounter power from your multi-class. At the point where your main class allows you to trade up that level 1 encounter power then you can also trade up the multi-class power you got in place of it.
But couldn't you retrain the multi class power swap feat at a later point to choose again which power to swap?
There's no need to retrain the feat. I was correct, but I forgot a caveat. You still have to swap out an equal level power. Each time you level up, you can swap out instead a higher level power for a different higher level mc power without any need for feat retraining.But couldn't you retrain the multi class power swap feat at a later point to choose again which power to swap?
But couldn't you retrain the multi class power swap feat at a later point to choose again which power to swap?
No, this in not correct.This is incorrect if you are talking about the power swap feats. Whatever power from your original class that you traded to get a multiclass power is the max level of the new power you can gain. For example if you swap a level 1 encounter power from your original class you can ONLY get a level 1 encounter power from your multi-class. At the point where your main class allows you to trade up that level 1 encounter power then you can also trade up the multi-class power you got in place of it.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.