Is any other distro moving to GCC5 so quickly? (Arch users?)
That said, I do wonder if this change is going to break more things for end users than they really bargained for. It reminds me a little of the Pulseaudio introduction - where in the haste to ship the new shiny ASAP, they ended up shipping a distro where a huge percentage of users never really got properly working sound. In this case, I'm worried that they underestimate the amount of stuff that users depend on but aren't included in the distro, and that many of these will break. Thinking of stuff like dropbox, the nvidia drivers, skype, etc.
I'm not certain that in retrospect this will be shown to be one of FESCo's better rulings, and that they would have done better to give companies like nvidia, microsoft and dropbox more time to adapt. But time will tell.
Debian has gcc-5 in experimental. A fact I'm taking advantage of because I want to get Docker working on my sparc server but gccgo is broken on 4.9.
It was fixed a few months ago in the gcc repository but the bleeding edge gcc repo has a broken libsanitizer on sparc. David Miller made some patches but gcc won't accept them(has to go through upstream) and upstream(llvm) have been ignoring them.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59758
So I'll have to disable asan or convince llvm to accept davm's patches and then wait for gcc to merge from upstream.
As far as I know, while your link shows that Debian is getting ready to provide it to its users, they haven't yet formed plans to use it to compile their packages.
Usually, my laptop can recompile @world (aka everything) overnight, so it's not too much of an issue.