Depends on a lot of factors. There is no engine oil, so the first scheduled maintenance will probably be the cabin airfilter (20000 miles in every car I've had that has one), and I would guess that anything in the suspension that needs grease will get the same interval (many cars have nothing to grease today but it is a possibility). Then there are tires.

Brake pads should last a little longer, but I'm not sure how much.

Ultimately though I believe electric cars will be much more expensive in the long run. Nissan wants $5499 for a new battery back. I don't know of any study on how long they last, but reading forums and extrapolating I would say you should plan on replacing the battery pack every 100000 miles. This of course depends greatly on how your charge it which in turn depends on how far you drive. If you drive the full range of the battery every charge you probably need to replace the battery every 50000 miles. If you make dozens of short trips per day, charging after each, you could potentially get several hundred thousand miles.

I'm curious about your A4 experience - how many miles were you driving. Unless you are driving 80,000 miles a year I don't see how you can get that high - at 80,000 miles/ year you have timing belt service. If you are driving this many miles the VW diesels (same base platform as the A4, though less luxury) can probably pay for the entire car including maintenance just in fuel savings.