That depends. You started this thread asking for Apple to provide a replacement for hardware they've discontinued with their next OS release. What if Apple never does so? Despite your, or anyone elses, preference for Macintosh / OS X if Apple doesn't update the Mac Pro you'll have no choice but to find an alternative solution.
SGI is a prime example...great hardware and a great OS. But they're no longer viable these days. Those who loved and used SGI's had no choice but to move off the platform. Mac professionals could be facing a similar fate. At over 900 days without an update if I were using a Mac Pro professionally I would be examining other solutions. Windows would be one of those solutions. A solution which is not nearly the problem some Mac users make it out to be.