:required validation in CSS3

Good day,
I have used :required in a HTLM5 form<label for="mail">Votre mail : </label><input type="email" name="mail" id="mail" required/>. It was understood by the navigators but in the validator instead of writing the following in my CSS3:  
:required{ background-color:pink;}:focus{ background-color:whitesmoke;}fieldset{ margin:20px; background-color:#FFEFD5;
}
I had to write the following in order that my CSS (level3) be validated.

[required]{ background-color:pink;}:focus{ background-color:whitesmoke;}fieldset{ margin:20px; background-color:#FFEFD5;
}
Could we expect that :required be validated by CSS3 validator in a very near future ? Or am I dreaming about it ?
I thank you for the attention drawn to this mail.
I look forwards to receiving you answer.
Yours sincerely
Benedicte