My son is just finishing yr7. He left a very small independent school and went into a massive state secondary, with an intake of 240 pupils a year. He knew not one child in the entire school and, to top it off, uses a wheelchair which can add another barrier when making friends.
He is also not sporty, into IT and quiet. It took a half term before he relaxed enough to chat to the other kids on his own. He now has one good friend and lots of other friends he can hang with, not just in his class. I actively encouraged joining clubs to help him socialise. He joined science club, chess club and signed up to be a student librarian twice a week during lunchtimes. This meant that, although it took a while to get a 'best' friend, he got very well known, very quickly and it forced him to socialise.
Although, it was one hell of an adjustment, he now loves it and is very excited to start yr8 soon.
The school are aware it might take some children a bit of adjustment and our school was brilliant and socialising the quiet ones.
Just tell your ds to chat to his seating partner in each class and very soon he will know a few children. Join any clubs that interest him and he will find like minded children there. At lunchtime, just go sit with his class group, even if he is quiet. You won't believe how much they change this year!
Good luck!
TL:DR? - It will be fine.