I think it's pretty obvious that Harry is gay, but it would completely destroy his fanbase if he came out. He would actually be breaking his contract if he came out, one can imagine. There are hundreds of thousands of girls obsessed with Harry who's worlds would be shattered. He can't come out whilst in 1D.
Anyone wondering why they have pushed the 'cougar' stories for Harry, well it's so it makes it easy for the young fans to think they still have a chance with him, and also the hate can focus on 'get someone your own age'. Also, the Caroline Flack thing was simple to pull off because she is a Syco employee, under contract herself to do and say anything they tell her or she's out of a job.