No-one knows. But per ITguy's comments, I've already begun my migration - to Linux.
The grief doesn't end with AWOL hardware updates. The software has been neglected too (except for iCandy features that I don't use). The Finder freezes over trivial things - I just now right-clicked on a file, resulting on a freeze, and in "force quit" it crashed instead of restarting, meaning that a reboot seems necessary. When I click on a file to open it in Preview, it frequently tells me I don't have permission (I do) - a multi-generational bug that Apple is too busy to fix. I could go on and on.
My Linux box (which I'm typing on) has a maxed-out Skylake and a GTX 1070 and cost about $1000 sans monitor. It's faster than any 4-core mac at everything and is rock solid. I'm on Mint 18 now (quite stable), and have Manjaro KDE Plasma on a different drive. The latter has a more modern and attractive user interface (though perhaps it needs another point update or two before full consistency is reached), and it has a very high degree of user control over its look and features. Linux is fun!
I still use both, and I haven't made a concerted effort to switch completely yet, preferring a more organic shift (and, you know, I still hold out some hope for a nnMP). But I find myself using the Linux machine more and more, with fewer and fewer application holes left to fill before it's a completely satisfactory replacement. With another few months of no updates from Apple, I may very well have left the Mac behind for good.
