I doubt it. Network effects matter and nobody is switching from LinkedIn for fear of missing out. There is no other work-related social network like it.
It's different with FB/Instagram that there isn't much at stake so people will just switch to test something and then stay. With LinkedIn, the "what if I miss a job opportunity?" factor means there's pressure to ignore the UI issues and just stick it out.
I don't see a disruptor in this industry, do you know of any?