I still think ia64 was sunk by the let-the-compiler-do-it tarpit. There were ambivalent aspects such as, at the time, questions of power or chip area. But things like memory latency are just not predictable enough to do strictly in-order pipelines. OoO won.
Had AMD not been around with AMD64, the industry would have had to get it working no matter what, HP and Microsoft were already on the Itanium train, and if production of x86 got slowly replaced by Itanium that was it, Windows and HP-UX would drag the ecosystems into it, and eventually the remaining issues would be sorted out.
UNIX systems, I also doubt, as we were still in the days each vendor had their own CPUs.
AFAICT, they expected Itanium to own the high end server/HPC market, while 32-bit x86 would continue supporting PC’s for another decade.
That seems remarkably short-sighted in retrospect.
For what it's worth, I followed Itanium as an IT industry analyst and wrote a short book recently on the topic. https://s3.amazonaws.com/bitmasons.com/docs/Lessons+from+the...