My 4yr old has continued to grow both upwards of at least 2" and outwards as of this year. She won't "officially" be 5 until the end of this month. She is finally coming into her mare body this year.
My just turned 3yr old on the other hand is still growing hard. I think she'll outgrow the 4yr old in height. That is the one I can't wait to see all filled out, or whether I just truly own a gangly plug headed giraffe.