It's been more than three years since Apple last talked about the Mac Pro and today Apple announced an upcoming refresh, with a modular design that can accommodate high-end CPUs and GPUs.
In the meantime, Apple is today releasing speed-bump updates to the existing Mac Pros. The $2999 model goes from 4 Xeon CPU cores to 6, and from dual AMD G300 GPUs to dual G500 GPUs. The $3999 model goes from 6 CPU cores to 8, and from dual D500 GPUs to dual D800 GPUs. The rest of the specs remain the same - there is still no USB-C and no Thunderbolt 3.
Apple is currently rethinking the Mac Pro concept, with the goal to deliver a new modular design that can accommodate high-end CPUs and GPUs, as well as Apple-branded pro displays to go with them. All these should be expected next year.
Apple is also working on Apple-branded pro displays to go with the new Mac Pros. These next-gen Mac Pros and pro displays will not ship this year.
Apple has also confirmed that new iMacs are in the pipeline, slated for release this year, including configurations specifically targeted at large segments of the pro market.