Zen 2 is supposed to be launching in the middle of the year, and it's conceivable that part could support DDR5, but AMD has made it clear that the AM4 socket is supposed to be around through 2020, and historically AMD has always changed sockets for a new memory type, which strongly suggests no DDR5 support. From Intel's side it's anyone's guess as their roadmap is a mess right now with 10nm their priority above everything else, so I'd say it's unlikely that they'll offer DDR5 support this year either.
Actually, AMD had in the past CPUs with 2 memory controlers, which supported 2 sockets, so in theory they could still maintain AM4 compatibility with DDR4 support and enable AM5(AM4+) with DDR5 support on the same CPU.
See for example Athlon II:
Propus (45 nm SOI with immersion lithography)
Athlon II X4 630
Four AMD K10 cores chip harvested from Deneb with L3 cache disabled[6]
L1 cache: 64 kB + 64 kB (data + instructions) per core
L2 cache: 512 kB per core, full-speed
Memory controller: dual channel DDR2-1066 MHz (AM2+), dual channel DDR3-1333 (AM3) with unganging option
MMX, Extended 3DNow!, SSE, SSE2, SSE3, SSE4a, AMD64, Cool'n'Quiet, NX bit, AMD-V
Socket AM3, HyperTransport with 2 GHz
Die Size: 169 mm² [7]
Power consumption (TDP): 45 Watts or 95 Watts
First release
September 2009 (Stepping C2)
Clock rate: 2.2–3.1 GHz
That being said, I think it is a bit too early for DDR5, although I'd really love to see some CPU which supports it.
I think DDR4 brings too little to the table, so personally I skipped platform upgrade, however DDR5 will for sure be different due to doubling of the data rate.