I think with a 680 your chances of getting off the waitlist have increased. A 680 is much closer to the mean GMAT so your profile is probably more in-line with the average student. Without seeing the rest of your application it is impossible to know, but the fact that you worked hard enough to boost your GMAT, and you are still within the application period means that you've improved your chances. So atleast you know u've done everything you can to help gain admission. Good work, and good luck!
From what I've seen with UCLA FEMBA, a lot of people make it to the waitlist with low GMATs. So hopefully your increase will pull you off. With the addition of the FLEX option this year, there might be a few extra spots! Good luck