DDR5 is still at least a year or two away, unless Intel is also looking to aggressively upgrade their 10nm products with it.
As for pcie 4.0 lanes that's from the CPU anyway, so dops that mean PR already has it?
Actually, the DDR5 standard is published next year, summer of 2018. GF 7LP incorporates support for DDR5. Because of this, it could be preparing for the future.
Another alternative is they are trying to help board partners sell more boards, as Intel does, but without cutting off generational compatibility, in an attempt to curry more favour and support from board manufacturers.
Another alternative is changes for Znand or licensing Optane.
As to it being from the cpu, it is easy to make it clear what minimum specs a board supports by creating a chipset revision. This can become a shorthand for features, such as pcie 4.0 (or 5.0, published Q1 2019) or DDR5, thereby aiding consumers.
Now, regardless of consumer availability, do you remember when Intel, years back, added dual compatibility to its HEDT line. Something similar could happen here.
In other words, many possibilities, no certainty.