I'm certainly not waiting for arc to become perfect. My side project may well end up needing me to reinvent a computing stack from scratch: http://akkartik.name/about. But I fully expect it to take 20 years, so don't hold your breath :)
Yeah, I'm actually constantly looking for shortcuts, ways to not need to reinvent the stack, ways to build things that will help existing projects, or allow people to use existing languages and tools.
When I said 20 years I wasn't saying I have a plan that's going to take 20 years. I meant that I'm building small projects that -- when I step back -- seem to be headed in that general direction over time. Projects like wart, tracing tests and layers. I'm building these little projects out in the open, so hopefully I won't fall victim to the "hacker comes out of basement after 20 years with a compiler and OS that nobody cares about" failure mode. No, my goal is to fail in some more creative way :)
I'm less worried about my goals changing. On the one hand, if they do they do, one can't be anything but fatalistic about it. On the other hand the goals I outlined above seem to have hooked into my motivation at a deep level. I may well end up switching solutions I explore, but it seems like the goal is unlikely to change.
I haven't really started building anything for the past couple of months, but I've been thinking lately about three potential little projects: a) a simple multitasking OS without virtual memory or processes, maybe even without preemptive scheduling, b) a better language for teaching programming by separating scope from the notion of functions, and c) an assembly language with structured programming and lisp macros somehow. Something 'easy' to build without needing an entire C compiler. Rephrased: "I'm willing to do my own register allocation. What can you do for me, lisp?" :)
Mostly I just get up every morning and work on whatever I want. And these are the things I've been ending up working on.