IMG over WIFI

[Tim Curtis]

It would be convenient for sure :-) but I'm not aware of any utility that can remotely image a running Linux OS and then transfer the image over the network to the host computer. If it exists I'd definitely try it.

As far as in-place updates go, its usually possible to offer these within a given release of Raspbian. Its when the project needs to migrate to a new release of Raspbian OS that the only option is a re-flash. The need to migrate is usually driven by a new Pi or capability only being supported in the new OS.

Here's a history of OS changes in the 4 series

// 4.4 2018-MM-DD
// 4.3 Update 2018-10-19
// 4.3 2018-09-27
// 4.2 Update 2018-07-18
// 4.2 Release 2018-07-11
- Raspbian Stretch Lite 2018-06-27
// 4.1 Release 2018-04-02
- Raspbian Stretch Lite 2018-03-13
// 4.0 Release 2018-01-26
- Raspbian Stretch Lite 2017-11-29

There is a new release of Raspbian dated 2018-10-09 but I'm not seeing a need to migrate to this yet.
https://www.raspberrypi.org/downloads/raspbian/

-Tim