Vega cannot do CUDA. The lack of CUDA means the MBP would be significantly limited for a large slice of professional work, i.e. computer science, engineering, etc. Other companies manage both NVIDIA and AMD solutions, with a fraction of Apple's budget.
And yes, if Windows or Mac laptops are released at the end of the year, after Turing is released (or Navi next year) but continue using Pascal or Polaris, then that would be ridiculous.
Sure, the CPUs will likely be the latest. But why the delay? And during the delay, how many other non-CPU technologies will be updated? GPUs are but one obvious example. Otherwise, the longer the delay, the less time before the next major tech release comes, resulting in Windows laptops again surpassing Macs.
Quad i7 + Vega M GH, 100W
https://ark.intel.com/products/1304...RX-Vega-M-GH-graphics-8M-Cache-up-to-4_20-GHz
Quad i7 + Vega M GL, 65W
https://ark.intel.com/products/1304...RX-Vega-M-GL-graphics-8M-Cache-up-to-4_10-GHz
Quad i7 + Iris Plus 655, 28W
https://ark.intel.com/products/137979/Intel-Core-i7-8559U-Processor-8M-Cache-up-to-4_50-GHz
i.e., for the low spec Vega, 65-28 = ~40W, or for higher spec Vega, 100-28 = ~70W.
Also, consider that if we are going to actually get a proper upgrade in CPUs, then 6-cores for 15" is a must. So unless Intel are going to be making special chips for Apple, some efficiency will likely be lost moving from a CPU+GPU on one die to a separated configuration.