Its hard to have a discussion involving hard facts/figures if you aren't specific, you talked about batteries in general, not Li Ion, I'm not arguing that we are at/close to the limit of the wh/kg on production LiIon batteries, but that isn't the only technology out there. Also, vapourware is hardly a fair term, it isn't theoretical or a concept, its capacity has been independently verified.
Granted I wasn't specific about LiIon, but that's what is going to be used for the near future at least (next 5 years), and it's pointless speculating about possible future alternatives till someone actually gets close to marketing it. However, since nuclear powered cars were suggested in the 1950's I'll continue to doubt such tech till it actually makes it to market. There is a suggestion that it's based on Silicon, which has been used before but suffers from longevity problems.
So you assume that at some point in the future, we'll all have EV's, but somehow rapid charging technology and battery capacity will have gone backwards from whats available today? riiight
No, but once a defacto-standard has been set it's often very difficult to displace it. Take VHS cassettes - inferior to Betamax, but still became a standard, and wasn't displaced till DVD's came out. 50Kw 'rapid chargers' seem to be becoming the same de-facto standard.
Someone also has to pay for the infrastructure. A few 50kW chargers at a single location isn't too difficult. A dozen or more 250-500KW chargers. Hmmm.
There is also little incentive for a charging station to offer rapid charging. If you're 'stuck' there for 30+ minutes then you're very likely to buy a coffee or even have meal. If you're in and out in 10 minutes you won't. They'll sell you the same amount of leccie regardless of how long it takes. Any 'extras' are extra profit. Given that many petrol stations have already turned into mini-marts where people do a months worth of shopping whilst I'm trying to pay for 70L of unleaded, what makes you think the charging stations want to allow you out quicker?
Anyway - Got my three B-2's at Fairford, plus a bonus C-5M. Currently at the Bristol ABS meet - billy no-mates. M4 is shut and all the roads around the M5/M5/A38 area are jammed solid so no-one else has made it. Either that or they forgot to charge their EV's