Question: You know C++? (interpreted as a programming question, what's the result of C++)
Answer: is it D?
No, I didn't miss the joke, but I was tyring to say that in 5-10 years we'll still be asking "Do you know C++?" instead of "Do you know D?". At the moment nobody is hiring D programmers. Besides, if D was as popular as Java or C++, then the joke wouldn't be as funny.