The X399 incompatibility with the new TR3 is my biggest gripe as well, especially given the relatively short half-life of X399 (as much as X399 and TR2 are supposed to continue alongside TR3). All that makes the Intel 10980XE -about 'half price' compared to 9980XE- very interesting, but X299 is not going on as flag-ship for much longer, either.
And frankly, I have been very happy with the performance of my 16c/32t 2950X which has an extensive (ambient) water-cooling system. At 4.3 GHz all core, tight-timing DDR4 @ 3466 and decent scores (per spoiler), it probably would make an immediate upgrade to 24t TR3 not really worth it. 32C (or even a later if/when 64c with the TRX80 chipset
) would be more interesting.
In any case, I want to see some real world TR3 and latest Intel HEDT tests first, and also wait out the inevitable 'agesa' updates...if launch bios issues of X570 are any indication for the TR3 launch, 'wait-and-see' is probably a good idea. That said, if there would have been X399 compatibility, I would have been much more tempted to act earlier...