You are not alone in these feelings, I felt this way a great deal and still do on occasion but I don't think what you think is truth is =)
Before transitioning I figured I was gay (I'm probably 80% gay 20% straight, so kind of Bi) but I 'became' bi when I got on T. The hormones change your attractions. I swore up and down to my therapist that I would never find woman attractive. But about 6 months into T I suddenly began seeing woman sexually, something i'd never thought possible. (Before transition I was disgusted by females, had no desire to ever think of them sexually, seeing a straight couple kiss in a movie literally sickened me...)
While you may not experience the change, it certainly is a possibility. I still prefer men but now I can look at a female and not think "Not if we were the last friggin people in the world" but instead "It could work..." Anyways, the point is, things could change.
Now if things don't change, really don't despair! There's a website/forum online that's actually a collective of men who are in relationships with FTM's (can't remember the name of the site to save my life though, sorry.) My current partner fell in love with me before I came out to him as trans, but during the period in which I was presenting (best I could) as a man. He's not really gay, but we are in a 'gay relationship'. Without going into unnecessary detail, the fact that I'm not 'complete' down there doesn't matter too much.
To say that no gay man will ever want you is a bit of a broad brush to paint with don't you think? Some gay men won't be into you, because all they care about is your body, but do you really want to be with those men? Others will understand and still want to be with you. Some guys just won't want to be with you cause you're not their type. Thats just how it is for everyone, regardless of whether your gay, lesbian, MTF or FTM.
Everyone is different, some men may be VERY interested in having sex with a manly woman. I think you can't just say "No X's likes Y's" if we all still thought like that, there wouldn't even BE "powerful, high earning women".
I personally will probably never have downstairs surgery. I'm comfortable right now with the use of prosthesis to accomplish my 'goals'. I also think you should maybe separate love from sex.
Will you be alone forever because you transition? Of course not. There's so many of our species in the world it's impossible to think that you won't find SOMEONE if you look for them. Will you be able to have casual sex with others if you transition? Well yeah, the base desire of our species is "fight vs flight" and "reproduce". Of course reproduction gets muddled since we have such a wide sexual scope in our species, but sex is a driving force. There are millions others of your species all around you, who almost all (with the exception of some) have a base desire to copulate.
Also with our current world, everyone is becoming so much more open to the LGBT community. I could probably go walk into a walmart right now, take a survey, and at least 50% of the people in there would not give two wags if I told them "I'm gay, what do you think of that?".
So in a nut shell, if you want to transition, and think it's going to make you happy, do it! Why not? You're not going to be alone unless you isolate yourself. You'll find people who want to have sex with you and if you look hard enough you may even find that special someone who wants to be with you for the rest of their lives. Human's are a species that seeks out the pack, you'll find someone. Just because your 'different' than a regular cis-gay guy doesn't mean no gay guy is going to want you. And if you end up becoming Bi thanks to the hormones, well I don't know a lot of females that would hate the idea that you can't get them pregnant.
You're not alone, i'm sure many others have felt this way too, I know I sure did.
Best way to get out of the no mans land you feel your in is to go out and make some new friends! At the start of my transition I joined a local club that shared an interest of mine. I've made many friends (no one in the club really knows i'm trans though) so recently I found a new love for Archery. I intend to buy myself a bow on my birthday (one month) and join a local range where no one knew me before my transition. I expect everyone will treat me like the new me and I will have many friends who like me for me, and not for 'the old me'. See what i'm saying? Find an interest of yours, set aside some spare time, go onto a website like meetup and join a local club and go out and have fun!
I was talking to a good family friend a couple days ago. He said I should bring my partner to our next get together (my family and our close friends. The big family on un-releated blood

) I told him "Well he's very social awkward" I'll never forget what he said to me for the rest of my life. He said "We all are in the end aren't we? Just a bunch of socialy awkward people. But that's why it works. We're all just human."
So go out there, transition if it's what you feel is right and make some friends! The point of it all, of everything is the little stuff, worrying about 'will they like me?', hating the weather, petting your dogs, running through the rain, driving to work. It's life, and it's worth living for and being a part of. So be yourself, the real male you and join the millions of us other socially awkward people.
Hope that helps some.
Cheers