C.H.
It could be that your older son is having jealousy issues. You might try spending a little more one-on-one time with him. When you're having to attend to your baby, talk to him so that your older son can hear and say things like, "You are so lucky to have ___ for an older brother. You guys are going to have so much fun together!" When you put the baby down for a nap, tell him, "It's now ___'s turn to spend time with Mommy." Make sure your older son hears you saying these things.
Also, when my son was a newborn, I started getting my daughter involved in all of my son's milestones. When he smiled or laughed, I would say, "Look, he's smiling/laughing at you! He loves you!" When he began to crawl and then to walk, I'd say, "Look, he's trying to crawl/walk like you. He wants to be just like you!" That makes the older one feel very special.
I also tried to foster a sense of love between the two of them by always having them give naptime and bedtime kisses.
Things aren't always peaches and cream at my house, though! Sometimes one hurts the other, and whether it was intentional or not, I always make the one who did the hurting hug and kiss the one who was hurt. Although my son isn't old enough yet to know how to hug and kiss, I kind of "help" him do it, and it makes my daughter feel better. Likewise, when she hurts my son, she knows that she has to tell him sorry and give him hugs and kisses. She doesn't really like it at that moment, but they're quickly friends again.
In short, no, your son will not always "hate" his younger brother. In fact, he probably doesn't hate him at all now. He probably just needs a little more "Mommy" time and some guidance on how to be kind to his little brother. Before long, I'll bet they'll be great friends!