From my past experience... if your needing to raise your GPA, wait until grades come up if you know they will be better. Yeah your application wont go out on the first mailing but if your gpa will be better it will more than offset that. If you think summer grade might lower your gpa i would submit before because the next time you will be able to update your grades will not be until the academic update which is opens at the end of year like november and you have until February to update so you have more time to offset lower grades if you worried.