From the article you link to: "Lithium ion batteries currently...

From the article you link to:
"Lithium ion batteries currently cost around $1750/kWh, however once Tesla’s Gigafactory comes online by 2020 this should reduce to $500/kWh retail." Sorry but that is delusional.
The post you link to seems to be from 2014 - a lot has happened since then. Lithium battery packs are already at less than $200 kWh (Tesla packs have been estimated at $190 kWh since 2016 - http://www.greencarreports.com/news...s-tesla-190-per-kwh-for-pack-gm-145-for-cells) - cell price quoted by GM is $145 per kWh (see previous link) with a pack price at around $215 kWh.
Tesla have recently announced economies of scale at the Gigafactory will reduce the price by 35% (that would reduce the pack price to around $125 kWh) - https://electrek.co/2017/02/18/tesla-battery-cost-gigafactory-model-3/
Flow batteries are good - however the only vehicle they've been tested in is the Quant (nanoflowcell) - they have not managed to produce anything other than concept cars since 2014 - much promise but a lot of disappointment. The scepticism surrounding Quant is palpable. There's a lot to be said for flow cell technology but it certainly isn't 'new battery tech' or cost competitive to current battery technology.

Solid state batteries seem the most likely next 'major breakthrough'. Toyota are working on both solid state and lithium air https://cleantechnica.com/2017/04/1...d-lithium-technology-ev-battery-improvements/
see this also:
http://www.toyota.com.cn/innovation...logy/next_generation_secondary_batteries.html.
It takes years from research breakthrough to market - lithium is good for some years yet and if lithium air can be commercialised it's game over for everything else - it has roughly 10 - 15 times the storage capacity of current lithium ion. https://www.sciencedaily.com/releases/2017/05/170517120733.htm
Dream on................