I feel like that and my pregnant friend who is due in a few weeks still feels the same. She knows one day she will have a teenager but she says herself she's so wrapped up in having a baby she hasn't thought and further.
I haven't thought about an older child and school age like even have tantrums and stuff to deal with but when the time comes I know I will expect it to happen. I'm not thinking in dream land I know you have hard work night wakings and such but I don't like to think of that I just think of a snuggly baby