Apple isn't going to release a new Mac Pro Tower until Kaby Lake Xeon is ready. Skylake doesn't support USB-C natively and hand-in-hand with the Mac Pro are the new dual USB-C and Thunderbolt 3 connectors.
http://appleinsider.com/articles/16...ential-2017-imac-mac-pro-kaby-lake-processors
http://appleinsider.com/articles/16...ential-2017-imac-mac-pro-kaby-lake-processors