Frankly, I can see why managed code is becoming such an ally to developers, but I think the most important thing to consider is the fact that there are millions and millions of lines of code in C++ already, where does that go?
As far as I can tell, I do see an eventual shift from C++ to managed code, but call me old fashioned I just love C++. But I, like most other people, want to do things in better ways than possible now, so the only question to answer is whether managed code will be better (now or in the near future), once that happens, no one's going to just want to stick to C++ because of tradition or because I love it.
As long as it proves to be a worthy successor, Managed Code is going to pave the new paths. But this will take time and no, I don't see C++ completely phasing out in the immediate future.
They are actually reconsidering the C++ Standard and I think in the next update the Boost library will be included, lets see how far they go to actually "compete" with the others (Java et al), if at all.