I'm going to have to hop in on this as well and add to the noise.
I've been using Debian since pretty much the very beginning (not quite - but REALLY close, just a bit after Bruce Perens left, but before woody), and it was my favorite Linux distro up until squeeze.
No linux distro has ever done more to turn linux from a serious piece of crap fit only for hobbyists and OS geeks than Debian, and no distro has ever had a larger fall. When Debian chose to pull that stupid stunt over Firefox/IceWeasel and then pile drive into the toilet with Squeeze (which literally fails on every computer I own, unlike Lenny), they proved that Debian's day had finally passed.
Ubuntu works. It works on laptops, it works on desktops, it works on netbooks and tablets.
RedHat has a completely solid place in the enterprise - hell, I'm converting 90 AIX boxes to RHEL 5 as we speak, on a project with timeframes more extreme than I can stand. But it *works*, and it's *solid*.
Is this a victory for OpenSource? Yes, just like the rise of "Open Systems" that pushed mainframes into the shadows and forced a radical re-thinking of the entire concept of IT. People used to pay for computing cycles, you know - before the days of Open Systems.
Android, RHEL, and Ubuntu are the result of the insanely hard work of the open source devs. But the devs have *always* sucked at dealing with users. Users want a phone. They don't give a crap who wrote it. Users want farmville. They don't give a crap why it works.
The age of the OS as a primary interface is coming to a close, just like the age of the teletype and the blinking lights was ended by the monitor. The Web Browser is the future interface (warts and all), and in this world where the OS is nothing but the chrome around a browser, Linux is far ahead. Users don't try to install software any more, they check to make sure their sites work and their WiFi is up.
Sorry for the rant. The point is - yes, Debian and Slackware and the rest are doomed to fade into the shadows to be replaced just like the systems and projects they replaced. I don't see you all weeping for CPM, or MVS, or IRIX despite the amazing things they contributed. The X11 project was dropped like a bad habit in favor of Xorg, and I can't even remember the last time I had to use CDE.
Time goes on. Simplicity reigns supreme, and if you're not leading the way on "just works" you'll get run over by someone who is. Debian still doesn't get that, FreeBSD doesn't get that, Slackware doesn't get that.