there feelings 4 eachother were always implied. and its fitting as Tifa had been flirting with Cloud all this time.Cloud could finally open up after Tifa unraveled his past in the life stream. so while i feel he was totally in love with Aeris, Aeris realised Tifa was right for Cloud, and in time Cloud too realised this, culmanating in that scene at the end of disc 2.

thats how i see it anyway.