I don't think being trans is the biggest deciding factor in how many friends, or the quality of friends, most trans people have - at least, that would be my guess. Trans people tend to have less friends, but it's mostly because of the baggage that comes from being as such ... like, trust issues, paranoia, prejudgement, low self-esteem, low confidence, or things like that.
If you're making friends now, you should be fine during and after transition; I'm less lonely than I was before transition, myself - and that's a fairly significant statement! I've definitely had a very small number of friends over the course of my life, and not even out of not wanting any; I'm just not good at keeping friends, I suppose. Though I am okay at making them, these days.