My daughter is 7.5 and is in speech therapy at her school. When we consulted the speech therapist last year, she said that once she reached her 7th birthday, she would qualify. However, the way she says "r" is different from most kids with an "r" issue. She only substitutes the "w" sound at the beginning of words, but when the "r" is in the middle or end of the word, it sounds like "eye" or "oy." So, for example, "board" would be "boyd," and "star" would sound more like "sty."
Apparently, the "oy" vs. "w" substitution made a difference in her ability to qualify for therapy because it is less likely for children to outgrow it on their own. The speech therapist said kids normally don't qualify for the "r" sound until later (I know I substitued the "w" sound for "r" when I was younger and outgrew it at around 7 or 8). BUT, she also said that she sees kids that are now 11 and 12 that still can't say it because they didn't qualify until later. So, I guess my point is some kids do qualify at age 7, so it might be worth looking into.