Xeon Phi coprocessors are flops competitive with GPUs and are used in many supercomputers.
Embedded FPGA accelerators are of interest primarily to large server farms and cloud operators, where the cost of development for FPGA acceleration is cheaper than the savings of acceleration-- Microsoft in particular has done a lot of work in this area (for Bing), and probably worked with Intel to define the CPU.
Pretty sure that Phi as you know it is largely being left. Argonne's Aurora exascale machine was suppose to be Xeon Phi, but it has been postponed till 2021 and will likely use some other tech. Also look at the top 500 list from late 2017. Trinity the NNSA computer at #7 is Phi based but only gets about 50% of theoretical peak.
Phi is dead. The next NERSC computer is GPUs. Not sure what Argonne is doing but there’s no reason to think it won’t be GPUs. The only reason Phi/KNL made sense was because it seemed like a conservative choice when GPUs were more exotic, which may have been okay if Intel didn’t have the crazy yield problems they had. FPGAs don’t make sense because the conservative choice at this point is GPU. I don’t think any of the leading compute facilities have the stomach for a new technology like this, especially from intel.
My personal tinfoil hat take is that Xeon Phi was made to make China waste top dollar on their supercomputers going with a less useful accelerator made by a US company.
Once China figured that out, the way they'd implement not falling for the same trick twice is simply never using US tech again. Which would limit other opportunities.
It's also at least plausible that they'd probably have people trained to think like Americans who might think of the same thing in advance.
Yes US government has forbidden the export of Xeon and Xeon Phi to China's supercomputing centers. It prompted the construction of Sunway TaihuLight, which uses Chinese own CPUs.
Embedded FPGA accelerators are of interest primarily to large server farms and cloud operators, where the cost of development for FPGA acceleration is cheaper than the savings of acceleration-- Microsoft in particular has done a lot of work in this area (for Bing), and probably worked with Intel to define the CPU.