A bit of "Monday Morning Quarterbacking" , but at least back to the topic of the Mac Pro but ..... It is puzzling why Apple didn't prepare a "plan B" about 1-1.5 years ago that could have used these as replacements for the current Mac Pro. It wouldn't have been an "omg it is better than sex" product, but it would have been something Apple could limp along with for another 1-2 years while they figure out what they really want to do.
In 2012, Apple 'bumped' the CPUs to show that they had something (even if it was just new firmware and slightly different order from Intel. ). Price cuts only is indicative that they weren't working on anything. Even entry level GPUs for the new machine. Extremely strange if the something like the 570-580 wasn't at the "entry level" spectrum of what they were working on up until it failed. I get how the "top end" GPU offerings failed, but how on Earth did the entry-mid level ones all fail also ???????????? Seriously.
A D510 (RX 570 ) and D610 ( Rx 580) wouldn't be a huge hassle thermal wise to put into the current system. Actually, they probably would get less failures because these are designed to run on the thermal zone that the Mac Pro provides and are pretty close thermal match to the E5 v2 limits.
[ Redoing the Xeon E5 to v4 would require the CPU board and blackplane board ( with PCH) changes which propagate more widely and get more expensive. But doing two more GPU cards. That isn't a huge leap. ]
Those would not have solved all of the problems outlined in their roundtable sessions, but it certainly would have addressed their major problem that folks don't believe they "care" or that they are doing anything substantive other than just cashing checks. No Plan B. No action..... really doesn't get solved by telling folks going back to hide in a hole for another year or two.
As for AMD's marketing, you can tell from the photos they are primarily marketing these card to folks with 3-4 years stuff. ( Not RX400 or anything much in last two years; just older stuff and low end iGPU. ) That's kind of the point though in the Mac Pro context .... it is an older system from that timeframe. Not sure the AMD move of shifting RX 4x5 to RX 5xx is going to work so well. They are going to get widely 'flamed' for this. That is probably going to get in the way of their advertising in more than few places. It is in the "doing something" range but they had already announced a xx5 update path... just use it. More smoke and more mirrors isn't likely going work too well.