Hi and welcome. I don't want to worry you more but wonder if you have ever considered if he may have Aspergers or aspects of it, many of these conditions can overlap and it does sound as though he may not 'get' social rules, turn taking in conversation etc. The good news is that if there is a reason behind his difficulties there is a lot that can be done to help.
My son has quite severe autism and has support for social skills in school - he has little speech and needs a lot of help. His support staff set up structured activities with the other children - they will take a typical playground game and break it down for him and teach it in small bits and then put the parts back together once he understands the expectation. You can also use play scripts initially to help e.g. teach him what to say in certain situations. Also teach him how to limit talking about one topic so as not to alienate other children. We do playdates where an adult 'runs' it eg we bake or make something / do something structured rather than let the children just go off and play. Just one child and keep it short eg one hour.
My son is about to go into year one and because there is a lot of understanding among the staff and children that he is different and there are reasons behind his differences the children are not just very accepting but actually really look after him. Despite hardly speaking to the other children at all he is bizarrely very popular. There has been no bullying at all.
You can read up about aspergers on the NAS or Ambitious about Autism website and see if any of what is described fits. Even if it is not Aspergers children with other difficulties eg dyspraxia, speech problems can often show some of the social difficulties that children with aspergers do. And the same techniques to address social issues can be used.
Often these problems will not resolve on their own. You can teach social skills to children who do not pick them instinctively, but obviously that does require recognition that there is a genuine delay or difficulty which school needs to address. I would suggest you discuss your concerns with school and ask them what they can do to help him make friends and whether they will consider putting in place specific intervention to help him. Perhaps arrange a meeting with the new teacher and SENCO. You could ask for a TA to support him at break time.
I would also tell the teacher about the negative reactions from the other children and ask what the teacher is going to do to address these. In a way its not the other children's fault, they just don't understand, but the school can do work on this to help the other children be more understanding. You probably won't win over all the children, but there will be some children who will go out of their way to look out for yours.
The game to avoid him is bullying and needs to be stopped.
To be honest the reception teacher should have picked this up and its concerning the school has not done something before now as reception is all about social play and identifying children who have delays.