I really don't think that asset streaming is dead, but 5 GB/s is much, much more (especially compressed) than GPUs can really handle as some stuff must always be inside of the memory because access times of the SSDs aren't that fast. Other things (like shadow maps etc) are made and hold in memory so even if the whole screen changes, not that much must be transfered. It is not like the whole RAM must be filled with assets etc.I just hope, the full on asset streaming dream is not dead. Cerny was clear on needing 7gig to compete with internal.
On the other hand we do know that compression has advanced since inception….possibly bridging the delta.
E.g. it would really be interesting to see how R&C would work on a PC, than you could try to scale the SSD speed down and test where the break-even point lies. So far I would guess it is in a range of about 1GB/s.