It won’t be too long before C++ reaches feature parity with Common Lisp ;-)

Seriously, though, CLOS and MOP are one area where CL performance isn’t great, so it would be nice if the CLOS implementations can take some inspiration from C++ here. Unfortunately, I don’t think the features that make CLOS/MOP slow are included in the C++ proposal, so I’m not sure how much it can help.