In my post Saying good bye - Microsoft is dropping Itanium I layed out Microsoft's history of supporting and then dropping processors based upon their high volume/low value go-to-market strategy. As several readers pointed out to me, Red Hat has also announced that future versions of Redhat Enteprise Linux will not support Intel's Itanium (see Itanium Support in Enterprise Linux for more information). Red Hat's announcement was made back in January. Novell's SUSE continues to offer Itanium support and is a lifeline for Linux users having a continuing requirement for Itanium support.
As with Microsoft, Red Hat has supported and then dropped low volume microprocessors in the past. For example, it dropped support for SPARC-based systems when REL 7 was released.
System software suppliers are often asked to support many different processor architectures. Some operating systems, such as UNIX and Linux have a long track record of multi-platform support. That being said, as sales volumes drop below a certain level, it is no longer economically feasable to continue supporting a product.
One benefit of an open source model, however, is that the proud owners of these systems have access to the operating system and open source application source code. Should they continue to have requirements than only these systems can address, they could continue, at some cost, to use and support them. The same can not be said of those wishing to continue using a closed source operating system. When the supplier declares that it is dead on a certain date, little or no support is available afterwards.