To be fair, this bug looks like it mostly affects systems that run lots of untrusted code -- e.g. cloud services. If you are only running code you wrote, that does not require many syscalls (compute heavy), in your own data center (or whatever), discounted Xeon chips that suffer from the flaw could be a good deal.
People who need to get absolutely the most bang for the buck have no ties to any given supplier. Cray deployed one of the first Opteron-based supercomputers.
Intel got lots of datacenter business simply by having a better (as in "better suited to our demands") product than anyone else in the segment. AMD has a short time window to make some large sales. They have until Intel ships a microcode fix or a new line of processors.