Update: Nani will be wearing the adidas F50 Adizero.
For your information: Both, United and Portugal, are under sponsorship deals with Nike.
When they say be a symbol for them, they mean it by making him wear two jackets and one pair of shoes displaying the adidas logo quite blatantly. Nani will be wearing the adidas F50 during his matches.
Nani visited the adidas headquarters in Herzogenaurach, Germany to meet his fans at the Adi Dassler Sportplatz and visits the adidas Walk of Fame and adidas Originals. Here are the videos from Herzogenaurach: