Based upon the rival's appearance, I don't think he'll be another Silver. He definitely looks like he'll be cocky and confident, but I don't think he'll be the type of trainer who comes off as rude.
I hear he's another childhood friend rival, so here's how I can picture him in the games, or at least how I'd like him to be. This all depends on how far GameFreak is actually willing to play with the rival's development. Anyway, growing up as friends he's always been the lesser version of you in the eyes of other people at school and home. At some point in time, the friendship grew distant as he started to become jealous of all the glory and attention you received. That's when he gradually changed into more of the loner type and started to do things on his own so people would stop comparing him with you.
When his younger sister was born, she started to idolize you more like an older sibling than her own brother. This is what really sends your rival off the deep end. He swears to himself that he'll be better. He swears to himself that he'll be better than you, and that he'll finally receive the recognition he deserves and that his sister will admire him more than she admires you, as nothing hurts more than when your own family praises someone else and sort of ignores your accomplishments in light of someone else.
So he ends up this cocky and confident character, but really he's just an insecure trainer searching for the recognition of his own accomplishments rather than be compared to you all the time. That's when he falls into the hands of the [secretly sinister] Professor Akuroma, who gives him all the attention and praise he's always wanted growing up. Your rival finds comfort in the attention he gets from this highly recognized professor, but really the professor is just using him to advance on his own evil plot.
By the end, your rival comes into the light of what the professor has been up to with him all this time, and when all is done and over with, he finds the real truth in himself and a new sense of confidence. A confidence that he is good at something [what that is, I have no idea yet] and that he will continue to get better at it. He realizes that he no longer has to compete with you to be better at everything, but that he is talented in his own skill and will work on improving it. This is where he receives the right type of recognition from others, and more importantly his sister and family that changes him to be a better person, and of course, a better friend to you.
All that said, the chances of this actually happening are probably slim to none!