Developing Portably, For the Future

If I were to start a new project today, what language and environment would I write it in? (Assuming I'm not targetting an environment that makes the choice for me (Android, iOS, browser-side javascript).)
So, let's say I'm doing some data processing or some web serving. I'm writing a command line tool or daemon. I think I'd like it to be portable between my Mac and Linux machines that I own. I'd like to not regret my choice of environment if I'm still using this thing 1-5 years from now.
What's in?
C/C++, Python. I am almost ready to concede adding JavaScript to this list, but I don't actually like the language, though I'm fine with using it when I need to for getting things done in browser UIs. These languages I believe will be solidly supported into the future and remain free of deathspiralling suck. The Python 3 transition is going slowly, but I think it could yet turn out okay. I wish Python had static type checking. C++ has lots of stuff added in the last 10 years that I don't want to use.
What's out?
Java - Oracle seems to be killing it. Damn shame, a few years ago I called it my favorite language.
C# - Microsoft actually made a decent language, I've been using it at work lately, and they did some decent things about pushing it into an open-ish standard. But I don't see any compelling reason to use it and I haven't heard that I can rely on the Mono framework to be reliable now and into the future.
PHP, Ruby - I hear nothing but grief about using these. I dislike PHP as a language and an environment. It's amazing that things like mediawiki and drupal are built on it, but I'm disinclined to hack on them because of PHP.
perl. Been there done that. I use Python now.
Any functional language. They make hard what is easy in other languages.
What's left?
Go - Google has a cute little language there. It has my favorite features checked off like: compiled, bounds-checked, and garbage-collected. It's BSD licensed, so no one company can kill it the way Oracle is doing to Java, but I feel like it's not ready yet. Also it's a kinda weird little language and there are a few major language features that I feel if go had them I would be much more productive when using it. Another major language revision, and some growth in the community library support, and hopefully it'll be better a year from now.