My opponent is playing an exalted deck and I am playing Pyxis of Pandemonium. The exalted text reads:
Whenever a creature you control attacks alone, that creature gets +1/+1 until the end of the turn.
After my opponent declares attackers but before we move into the declare blockers phase I activate Pyxis of Pandemonium's second ability:
Each player turns face up all cards he or she owns exiled with Pyxis of Pandemonium, then puts all permanent cards among them onto the battlefield.
As a result my opponent gets permanents that have the exalted ability. Will these newly created permanents exalted ability trigger or have they entered the battlefield too late? Does my opponent have the opportunity to change his attackers as we are still in the declare attackers phase? (not to the new creatures however as they will have summoning sickness)