That´s what we thought in the early 80s. And then all those portable electronic devices came along (who remermbers the IMB PPC...) and all of a sudden there was another revolution in battery technology. Who would have thought about an e-book reader less than a quarter of an inch thick with a battery allowing weeks of operation...
IMHO, Volume, you are mixing up here the phantastic progress in microelectronics (and its associated power consumption) with the quite limited one in battery technology.
Indeed, the typical Ni-Cad of the early 80ties (I remember some from the sixties) had 60 Wh or so per Kg. The numbers of the 1990ties NiMH are 110, and 160 are the one's of present Li-ion. See what I mean: barely a factor 3 in 30 years (arguably up to a factor of 5, if you totally disregard price).
A propos price: I considered to replace two 105 Ah 12V lead acid batteries (worth 2 x 150€ in my boat, however my shipchandler prizes 2499 € for the 24 V 104 Ah Lithium Battery that weighs indeed 40 kg less, of interest for
racing, sure, but way too expensive.
In conclusion, I fear that the opinion expressed in my initial post may well be valid.