La ISA IA-64 was born almost dead. There have been a lot of jokes in the past about this Intel architecture and its Itanium microprocessor. When the first AMD Opterons appeared, they crushed Intel's Itaniums and Intel put this project aside a bit to focus on Xeon, eventually releasing only the occasional update for the systems that depended on it. Behind all this is an interesting story that may be told at another time and that has several involved (see HP vs Oracle case, with Intel in the middle) ...
But now I'll just focus on the news about upcoming Linux 5.4 kernel support and the disinterest in continuing to support and maintain Intel's IA-64 architecture. By the way, don't worry, it won't affect you unless you have a supercomputer at home. Many people confuse IA-64 with the 86-bit x64 extension and it has nothing to do with it. The AMD64 (also called by Intel EM64T or x86-64) is a different ISA.
All the confusion comes because Intel called the x32-86 IA-32, and many think that the x86-64 is known as IA-64. But no, this ISA is specific to Itanium (or Itanic, as many jokingly called it for sinking like the Titanic). The truth is that it will affect the large machines that are still using it, such as some that HP, SGI Altix, etc. still maintain. But Intel is well aware of its failure and announced last year that it would stop manufacturing and shipping its replacement chips in 2021. HP has pledged to support its customers through 2025.
The Linux 5.4 kernel will bring a new driver for SGI systems for Origin, but will stop supporting SGI Altix. Weird, because Altix is newer than some Origin. The reason is precisely the reduction of IA-64 support. Packages for IA-64 have already been in decline for years, and the kernel will join this trend with release 5.4. For example, it is already deprecated for the GNU GCC 10 compiler, and if Linux joins now, it will be the final blow.
By the way, as a curious fact, to say that the elimination of support for SGI Altix will imply a cleaning of the kernel code and the drivers that will be eliminated that will mean the elimination of about 40.000 lines of code. That will lighten the kernel quite a bit ...