By the time the next model comes out EV battery technology may have improved, but unless batteries are cheaper by then it means the Jazz will be to expensive for it's usual target market (it's already gone that way to an extent with the Mk 4). They would be better off having both options as other manufacturers have already done, ie hybrid and EV choices.
We already have an EV as a second car and it's great for local trips and cheaper to run than the Jazz. However the Jazz is better for longer trips, we regularly go down to Cornwall and there the EV charging infrastructure is very sparse, the south-west is generally pretty poor for coverage. The driving experience is very similar for both cars so I don't think many people would be willing to pay for example an extra £10K for an EV version of the car, the only advantage would be the lower running costs. It will happen eventually, if the infrastructure improves rapidly in the next three years (and not just in London and the south-east) then it would have a better chance of success.