"Prediction is difficult, especially about the future".
But this is what Apple said:
"These next-gen Mac Pros and pro displays “will not ship this year”. (I hope that means “next year”, but all Apple said was “not this year”.) In the meantime, Apple is today releasing meager 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 D700 GPUs. Nothing else is changing, including the ports. No USB-C, no Thunderbolt 3 (and so no support for the LG UltraFine 5K display).
But more good news, too:
Apple has “great” new iMacs in the pipeline, slated for release “this year”, including configurations specifically targeted at large segments of the pro market."
From the article I linked.