Dead as a doornail, practically/unfortunately. Thanks to Sony, et. al. (yeah, they had lots of help) it's almost all over but the shouting. They just haven't announced the time of the wake...
The first thing to remember is that it's a business - it's not really about the sound, it's all about selling units to consumers. The business plan and execution never made great sense, but the Sony name (along w/ some others) carried things pretty far, considering how much money was or wasn't changing hands. And with the relatively tiny numbers for SACD (and DVD-A) the only real hope is that a niche market survives. That will cater to the relatively few enthusiasts, but it will likely never reach the mass market numbers needed to make a real lasting go of it.
Like the comments earlier, it's the convenience that's #1. CDs went so far & fast because of the convenience - the fact that the sound was better than cassettes was an added bonus. And that's the bigger hint of why SACD is dead - you simply can't use 'em in your car. You can't play pure SACDs or the hi-rez level on hybrids, and anyway why would you want to (if you can't hear the difference at 60mph and your Yugo doesn't have 5-channel surround)? MP3 quality (no oxymoron jokes here, please) doesn't matter at 60mph, it's perceived as convenient, and so 99%+ of the population prefers MP3s to SACD. Add in the licensing greed/insanity, and you had a recipe for almost guaranteed demise.
The hottest consumer item around is the iPod (and similar MP3 players). Adequate quality for the 99% (that kinda defines a mass market ;~) in a convenient package, w/ great marketing - and everyone wants one. Can you buy a portable SACD player? A SACD burner? SACD iPod? Sorry, but SACDs (and their megabuck players) will be fading away as the unfortunate but logical outcome of a lot of lousy business decisions.