It is still considered as a Bronze bakugan. Similar scenario to Special Attack. If you use a trap on a Special Attack bakugan then it will change attribute but its special treatment status as "Special Attack" does not change.
That would actually be a cool idea, a trap that changes a normal bakugan to a special treatment, but it would also add a lot more confusion to the rules, oh well...
Just saying before this is set in stone, we need official rules, like when is a trap to be played, cause if its at the beginning, than only string winds blow or prismatic magnifier can be played, it is risky though using 2 abilitys and 1 trap for one battle, you would have better luck using 1 ability at a time and activating another one if neccessary, but the amount of g's is magnificent.
It would work if you can pull off an ability-reviving technique afterwards.