Intel might face some competition but in my opinion they have just gone too far to catch in terms of the technology. Now the question is how they would capture the imagination of the consumers to gain control of the tablet/ultrabook segments.
These are old Pentium III cores. No instruction level parallelism, no out of order execution, etc. Only I/O interface is PCIe. Only advantage this has is the tool chain and that you can prototype your code on normal multicore x86 workstations and move to MIC later. Plus, the cores can work independently. GPU cores can't really work on separate processes. They are too interconnected.
For HPC, very little has been "abstracted away" since C was invented. Only the first four languages you list (plus Fortran) are actually used for HPC. Intel is promising the ability to use one (mature!) language/compiler/toolchain for both CPU and GPU/MIC code. This wouldn't be practical if the hardware wasn't x86(ish) ISA.
who care anymore what instruction set is used in HPC. when programming in C / C++ / cuda / opencl / java / perl / and a few hundered programming languages ... all that is abstracted away. code will have to be ported in either case (from intel single thread to intel multi-thread, MIC or OPENCL/CUDA). if you are going to go through the effort of porting, ISA is not that important a factor. install cost, operating cost, tools availabity, feature support, perf/$$ are more improtant. don't buy the intel hype. MIC is still just a research project @ intel. You can actually buy AMD and NVIDIA products with 3rd party tools support.