Currently, the vehicles are using 25 Ah cells, but VW provides an outlook up to 36 Ah.
As it turns out, increasing the battery pack in e-Golf by 44% (by using more energy dense cells) from 24.2 kWh to 34.9 kWh would increase NEDC range to 265 km or 165 miles.
Because NEDC is optimistic and typically real-world range is significantly lower than NEDC, to have a true 150 mile e-Golf there would be need to be at least 40 kWh (65% increase).
Volkswagen's Future Mobility PDF:
http://www.volkswagenag.com/content/vwcorp/info_center/en/talks_and_presentations/2014/07/FM_04_07_14.bin.html/binarystorageitem/file/06_2014-07-04+Presentation+Barclays+London+Steiger+TOP+COPY.pdf
Full article on InsideEVs:
http://www.insideevs.com/outlook-of-volkswagen-e-up-and-e-golf-range-with-larger-battery-packs/