Nobody needs to build valgrind for rust (or your favorite alternative). Leveraging existing libraries isn't trivial, but it's not a year long project either. IDE's support a lot of languages out of the box. rust support will be rough at first, but quality will be proportional to use. I suspect microsoft could build the layers you want like they did with J++ very quickly. A year? maybe 2?
The biggest bottleneck, imho, is developers. I don't think many people really know all the dark and scary corners of C++, but there are a ton of people that can get stuff done in C++.
If schools start graduating people with rust experience, the writing is on the wall for C++. Shifting school curriculum takes a big reason. Maybe a hit indie game, maybe some other killer app. I don't think servo is the one.
Really, it's a testament to the quality of the language that the complaints are all along the lines of "it's fantastic, but the tooling..." Don't underestimate that. Tooling can happen real fast.
Is rust a sure thing? no. absolutely not. does it have a chance of becoming the systems programming language in 10 years? Yeah. i think it does. i think it's got better than a 5% chance of doing that. 1 in 20 is a perhaps an insanely high number. The language is just so very good.