I'm pretty sure your school will tell you not to wait, well I hope they would. I wouldn't wait. I say get certified, get some experience under your belt in actually coding (or more if you do have some), and get the ICD-10 training while doing all of this. Either way everyone in the healthcare industry has to learn ICD-10 and knowing it before it's implemented can only be a plus for you, but I don't think you need to hold-off certification until it's implemented. No, get that as soon as you graduate.
AHIMA, which is who gives the CCS designation, is still training with the ICD-9 books and testing with them too. If I'm not mistaken they're also teaching ICD-10 with the course. The ICD-10 doesn't go into effect until October 1, 2014. You'll be taking the certification test with whatever books your class has specified, and I'm pretty sure it will be w/the ICD-9 until ICD-10 has actually been implemented. Knowing ICD-9 will only HELP you while training and transitioning over to ICD-10. I know the AAPC is making it mandatory that all of us who are certified through them (coders) take a test to prove we're proficient in ICD-10, which they're giving us until 2015 to complete. Not to mention the ICD-10 counts towards CEU's, from my understanding, but as far as a designation to say which you were trained in, that I haven't seen or even heard about happening with either AAPC or AHIMA.
Check with your school about all of this as you're currently in the course and I'm sure the instructor/adviser can help guide you too.
As far as what employers will prefer. When ICD-10 has been fully implemented, I'm more than sure all employers will want to ensure you're trained and proficient in it as a coder, thus AAPC requiring it, and I'm sure AHIMA isn't too far behind what they'll require of coders already certified. But until ICD-10 is implemented employers will want coders with experience and knowledge of the systems currently in place.
Edited for clarification.