The big problem here at this point is not individual innovation into new devices. We already have folding scooters, folding bikes, bike share, scooter share, etc. I already combine a folding scooter with public transport in Munich and it works fairly well for me for many trips.
The real problem is that in many cities, the infrastructure to support these things is extraordinarily terrible. For example, there are literally zero cities in the US with decent bike infrastructure -- and it's bike lanes/paths that fit the kind of devices you're talking about -- let alone good infrastructure. The city I'm in, Munich, hits the decent mark, but still has a ways to go before being 'good'. And it only works well for me because I'm a relatively healthy/fit adult, an elderly person or a child would have more problems.
If there was a sci-fi hoverboard that could be used in rain/snow to easily connect to the nearest public transit node, and easily carried until disembarkation, then car use would decline.
On a different tangent, I am curious about societies where motorcycles are a significant fraction of private transportation. What's their outlook on self-driving cars?