While some mobile SoC manufacturers have created their own graphics architectures, others license from ARM (and some even have a mixture of each within their product stack). There does not seem to be a specific push with this generation, rather just increases in the areas that make the most sense. Some comments tout increased energy efficiency, others higher performance, and even API support got a boost to OpenGL ES 3.1, which brings compute shaders to mobile graphics applications (without invoking OpenCL, etc.).
Three models are in the Mali-T800 series: the T820, the T830, and the T860. As you climb in the list, the products go from entry level to high-performance mobile. GPUs are often designed in modularized segments, which ARM calls cores. You see this frequently in desktop, discrete graphics cards where an entire product stack contains a handful of actual designs, but products are made by disabling whole modules. The T820 and T830 can scale between one to four "core" modules, each core containing four actual "shader cores", while the T860 can scale between one to sixteen "core" modules, each core with 16 "shader cores". Again "core modules" are groups that contain actual shader processors (and L2 cache, etc.). Cores in cores.
This is probably why NVIDIA calls them "Streaming Multiprocessors" that contain "CUDA Cores".
ARM does not (yet) provide an actual GFLOP rating for these processors, and it is up to manufacturers to some extent. It is normally a matter of multiplying the clock frequency by the number of ops per cycle and by the number of shader units available. I tried, but I assume my assumption of instructions per clock was off because the number I was getting did not match with known values from previous generations, so I assumed that I made a mistake. Also, again, ARM considers their performance figures to be conservative. Manufacturers should have no problem exceeding these, effortlessly.
As for a release timeline? Because these architectures are designed for manufacturers to implement, you should start seeing them within devices hitting retail in late 2015, early 2016.