What exactly, did Yitzchak now mean when he said, "Atah Zeh Beni Esav"?
Rashbam: It was neither a question nor an answer, but an assumption - According to the facts that were now available to him, Yitzchak asserted that it was probably Esav, on which Yaakov commented "I am."
Ohr ha'Chayim #1: Yitzchak acknowledged that he is Esav, and Yaakov answered 'obviously, it is me!'
Ohr ha'Chayim #2: Because there was conflicting evidence about who it was, Yitzchak resolved to bless the one in front of him (even though he concluded "Beni Esav").
Malbim: This was to clarify his identity before blessing him.
Ha'amek Davar: This was to arouse love for the one being blessed. Mentioning the name arouses love ("Midei Dabri Bo Zachor Ezkerenu" - Yirmeyah 31:19), and he also kissed him (27:27).