How exciting! / I'm so thrilled! / Can't wait!
Ilusión in Spanish means excited anticipation, not illusion. ¡Qué ilusión! expresses joy and eager excitement about something coming up. Very warm and positive.
—We're going to Paris next month. —How exciting!
I'm so thrilled to see you after so long!
—You've been accepted onto the programme. —I can't believe it, I'm so thrilled!