I am having another boy. My oldest DS is 2 so we have had to buy very little. We chose not to have another shower as we had a huge one the first go around. My coworkers are having me a small "sprinkle" at work because I started there after my first son was born and they said that they had never had one for me.
We did a small gender reveal for family and a few close friends (no gifts). However, I have had several friends and family members ask about our shower and were actually surprised that we were not having one.
I don't mind to go to a second baby shower under certain circumstances such as my friend that had another baby after seven years of not being able to get pregnant. Much of her baby stuff was dated.
I agree with the others that you should do whatever is acceptable in your circle of friends. I know that many of my close friends/family have bought or will buy for the baby anyway.