I don't know about the i860, but accelerator cards for math-heavy workloads are still a thing, of course. I remember seeing a brochure for an add-on card with one or two Cell CPUs, Intel has (had?) their Xeon Phi, and of course GPUs are very popular for things other than graphics.
Intel, for better or worse, are a victim of their own success. On the plus side, their success gave them lots of money to throw at the problem of making faster x86 CPUs. It seems, though, that Intel is gradually running out of luck, with AMD and now Apple introducing strong competitors, and Intel's advantage in fabrication eroding. So CPU-/ISA-wise, things could get very interesting in the foreseeable future.
I also believe that MMX was basically lifted from the i860, although again, i'm not sure.
It's funny, I tend to think of Intel as the boring chip company, due to the success and legacy that we like to moan about from ia-32, but they have actually made a fair few plays to try and move things on from there, fighting against the market which just wanted ia-32 compatible but faster processors.