Two things are for sure: the text of the loveletter shows beyond any doubt that he intended to send it to a living woman and the text also shows his ardent passion for this particular woman. These facts don't fit to a homosexual. Nevertheless the Sterba couple, psychoanalysts who had been pupils of Freud himself, tried to turn Beethoven into a homosexual, though he would have 'suppressed' these feelings. Nowhere the Sterbas 'accuse' Beethoven of having practized homosexuality. But according to the Sterbas Beethoven's 'misogynic' state of mind was a huge stumbling-block between him and the women. The loveletter, the Sterbas continued, is the result of his conflict between the platonic love for the woman involved and his knowledge about himself that he would never be able to become hers, to be her man in every respect. Later on Solomon and Wolf digressed on possible homosexual 'inhibitions' of Beethoven's personality. I find it not very likely.
See:
Sterba, Editha and Richard. Beethoven and his nephew. (New York, 1954).
Solomon, Maynard. Beethoven. (London/New York, 1977).
Solomon, Maynard. Beethoven Essays. (London/New York, 1988).
Wolf, Stefan. Beethovens Neffenkonflikt. (Munchen, 1995).