Isn't it the case that the Itanium architecture would not be vulnerable to Spectre because it moves the onus of branch prediction from the CPU to the compiler?
That was always the problem with the Itanium compilers. They were crap because they couldn't benefit from the years of tuning traditional architectures enjoyed.
Also the compiler had to be absolutely brilliant to rewrite the serial branching code most programmers wrote to work with the EPIC model. They had some good results optimized math-heavy code but the general purpose code ended up with too many nops waiting on results.