Some people are predicting the death of Solaris.
As a multimedia, client-side guy, I find Solaris to be pretty uninteresting, I find Ubuntu's attempt to compete with Mac OS X more compelling.
Solaris used to be a huge player on the web. When I worked for Geocities the whole site was run on a huge failover array of Solaris machines. Linux in 1998 was for hobbiests. It didn't start to seriously gain traction until after the "dot bomb" meltdown.
If Solaris does "die" then the start of its death could be seen with that meltdown and the subsequent rise of Google, they certainly have been a powerful "proof of concept" for Linux/ open source.
However with Open Solaris people can still use it to an extent, but I wonder if people think that Linux will "kill off" most other Unixes (at least commercial Unix) or whether you think Unix will keep going.
Certainly no one uses SGI workstations anymore, Apple effectively took the high end media workstation business from SGI.
That doesn't necessarily mean the death of Sun, but Sun won't let it go without a fight. Their basic claim is that Solaris is still the superior enterprise OS, and with Open Solaris you should be able to build clusters without having to pay licensing fees for multiple copies of it.
However with Open Solaris it would never completely die like Irix did, because it would still be available for hobbiests.