Yes, it is true, if all continues to go well, Pi will be having a baby sister. I've already started reading Siblings Without Rivalry.
The sum total of Pi's interactions with the baby:
At the end of February, we went to visit my folks, so Smitty and I told Pi about the baby because it was sure to be the topic of conversation amongst my family and we didn't want Pi to be blindsided. I told him that there was a baby growing in Mommy's belly and that pretty soon (hopefully) it would come home to live with us, and he would be a big brother! He said, "Like in Just Like a Baby!", which we had been reading a lot lately. He then went on his merry way.
When my belly started to get pretty big, probably mid-March or so, I said, "Look how big Mommy's belly is! That's the baby growing in there! Would you like to say 'hello' to the baby, Pi?" He touched my belly and said, "Hello, baby", and then he poked his index finger into my belly button and said, "What are you doing in that hole?"
On March 26th, we found out that this baby is a girl, and we told Pi shortly thereafter that this baby would be his little sister. A few weeks later, I asked Pi what we should call his baby sister. He did his thinking face (index finger to corner of mouth, slight head tilt) and said, "Hmmm...I'm thinking of a yellow flower." I said, "Well, since spring is finally here, the daffodils are coming up - daffodils are a yellow flower." He said, "Yes! Daffodil!", so we've been calling the baby Daffodil while in utero. I told Pi that when she comes out, we may want to pick another name, but I hope they have the kind of relationship that will allow him to use "Daffodil" as his special nickname for her.
Yesterday, Smitty really felt her kicking from the outside - he'd felt smaller kicking events before, but this one was unequivocal. Smitty asked Pi if he wanted to feel the baby move, and Pi ran away, saying, "No! I don't want to feel the baby move! Close up Mommy's belly!"
...and so it begins...