Solaris/SPARC is still going strong in large companies. One of the greatest advantages it has is that Oracle creates and supports the operating system, and Oracle creates and supports the hardware. (If you're running an Oracle database or some other piece of software, then that's an additional component that they create and support.) What this means is that if I'm having a problem, mundane or esoteric, I can go to one vendor and say, "Fix it." There isn't any bickering about what company's problem it is, and who manufactured my RAM, or any other the other silliness that crops up in vendor support. Large companies value this (as do us sysadmins). That also means they can do some very cool software tricks (which I'll mention a few here below).
The decreasing unit shipments is just as much a sign of virtualization as anything. Right now, I'm looking at an older T5240, with two eight-core CPUs which presents itself as having 128 virtual CPUs (execution engines or thread engines), and 64gb of RAM. This is by no means the biggest box on the floor. We carve these up into smaller systems using either Solaris Zones, or LDOMs. That's two different methods of virtualization with two different goals.
I did something great with an LDOM last week. I took a virtual server that was on the box and migrated the entire operating system and all the applications over to another LDOM... WHILE IT WAS STILL RUNNING. Aside from a quick (1 second) pause, the applications on the server had no idea that it just migrated to another piece of hardware while it continued to run. Slick! The original server had a failing DIMM. No worries, though even aside from ECC, the operating system automatically mapped out which parts of the DIMM were defective and retired the pages of memory so that they weren't constantly being exercised. Linux does all that... right? No?
Someone else, above, said, "I don't think you can have a zfs system fail and move it to different hardware like you can with vmware...". Nevermind that we can migrate a running operating system and application to another piece of hardware and keep it running. Yes, of course if you have a hardware fault, you can bring it back up on another machine. The virtualization with Solaris is quite capable.
In the environment of a large company where we're competing against Linux on the low-cost end of things, Solaris/SPARC is not only holding its own, but actually beating our Linux cloud counterparts in the costs of a virtualized OS/hardware. (I should ask my boss if we can publish a paper on this, because it is rather impressive.)
On the high end of things, we completely dominate. We generally use a T5-4 for our internal cloud (which really isn't the biggest Oracle server out there). It has 64 cores, presenting 512 execution threads to the scheduler. RAM goes up to 2TB. If someone starts out on a tiny box with only one CPU and 4gb of RAM, we can scale them all the way up to the top by increasing their virtualization settings. No migrating to different or unusual hardware. If an application team can't scale their code horizontally (hey, it happens), they can go way vertical in this configuration. We haven't had a need yet for an M6-32 (32tb of RAM, and 32 of the 12-core CPUs (3072 execution threads or "virtual cpus"). We have Linux surrounded (on the low-cost side and the high-performance side) in a large enterprise environment, and that's why Solaris is still there.
Now, I'm not an Oracle salesperson. But if Slashdot ever did an AMA with an Oracle sales engineer, I think my fellow Linux admins would be particular impressed on how far ahead Oracle/SPARC is in a number of key areas.