True, insofar as noone who is now married is likely to be directly affected. After the institution of marriage changes, the people of future generations will be affected.
I believe you have insufficiently looked down the road. There will be lawsuit after lawsuit, and if the equal protection argument holds sway, judges will be forced to strike down any provision of marriage that applies only to heterosexuals.
It is a Pandora's box.
The US did the right thing with equal protection for race. In fact, SCOTUS did the wrong thing by not adhering to equal protection in their finding in favor of affirmative action.
We are amenable to egalitarianism. The allure of equal protection is extremely powerful, and its application even more so. The Equal Rights Amendment was sailing along toward ratification until Phyllis Schlafly was able to alert enough people to its dangers. We did the right thing there, and I hope we will do the right thing here.
No to the redefinition of marriage. No to the civil union equal-protection compromise. No to judges legislating from the bench.
All that said, I am amenable to civil union legislation that steers clear of establishing equal protection.