No, I don't think Tenchi is gay at all. He's just indecisive and has so many girls living with him, he doesn't know what to do. If he were to make a definite decision, for me it would have to be Ryoko. Why? Because she seems to show the most interest in him next to Ayeka, who feels that Ryoko is just a shameless monster woman. I haven't got the third OAV yet, but when I do, it should be very interesting. If you would check out the Tenchi fanfiction website, I think in all the stories Tenchi is straight as an arrow.