If the days of quant are over, then why is there this website completely devoted to it and helping others along this path?
And this article I just read:
http://www.advancedtrading.com/managingthedesk/240000420
I think the point people are making when saying 'the days of quant are over' is that the need is shrinking for people to do complex math relating to derivatives. Such people are the only ones who were referred to as 'quant' in years past, now 'quant' has become a much more generic label. When I worked in a hedge fund six or seven years ago, someone in risk would not be referred to as a 'quant' nor was 'quant' considered a particularly attractive label to have. But maybe that shop was unusual, I don't know.
There will always be a need for people with varying degrees of quantitative aptitude in every industry of course. This website is a testament to the fact that there are still people interested in math and coding and want to work in finance, not to the fact that the jobs of yesteryear are returning.
If all that is meant by quant is that interest in math and strong computer skills and a tilt toward finance, then I suspect there will always be quant jobs. But you shouldn't take lightly that the financial world is changing and the subset of skills you need is a moving target (of course it would be quite a challenge to learn 'all of math' and 'all of computers' so you would always be competitive).
Per your original question, I would suggest take the CS course and learn Economics and Finance through autodidactics.
For Finance, a place to start would be Investments by Bodie and Kane.
For Economics, as a Math major, you should have no trouble starting with a text labelled 'Intermediate [Micro/Macro] Economics'. Personally I used Varian for Micro ; I don't recall what I used for Macro.
Additionally, Woodridge is a good Econometrics book.
Best of luck.