Curbside robotic delivery is basically the same technology as self-driving cars, which have already proven to be a viable technology. There are safety barriers to overcome, but we are a long way down the path to that being a reality.
With robotic delivery, the cost of providing home delivery take out meals is reduced significantly (much less people cost), potentially to a stage where take out becomes the more common than home cooking.
Combining robotic delivery with warehouse automation (e.g. Kiva Systems) would bring down the cost of home-delivered supermarket shopping below the cost of actually visiting a store, which would lead to significant uptake, and eventually the end of the supermarket.
Robotic collections, including those easily scheduled for hours when you're actually at home, would eliminate one of the frustrations of online shopping, leading again to greater uptake.
And, even if you're going to shops to view items, do you need to hassle of carrying bags of goods around, loading and unloading your car? Or will you elect to have to goods delivered to you? That which was previously a luxury becomes affordable with robotic delivery
Robotic delivery will become the primary way that goods enter the household.
So how will it work? An easy mechanism for the first generation would be to rely on cars, with the proven self-driving car technology. The car (or more likely a van) would contain numerous compartments accessible from the exterior of the vehicle. When the vehicle arrives at your premises it notifies you via call / SMS / tweet / etc. You would then go out to the road and type in a code into the vehicle (to ensure identity). The door of the compartment would open, and you would take your goods.
The second generation would be pavement based (probably more difficult to master than roads), but could deliver smaller goods to your front door.
Later generations could potentially deliver goods into your home, and even put them in your cupboards for you. But such feats would require very sophisticated AI, object recognition, not to mention a dexterous robot.