Probably a too simplistic question and may require more detail but if a user is connected to a LAN (not necessarily a Meraki one) and then unplugs will he need to re-authenticate if the SSID he connects to is in Bridge mode and the client IP addresses for that SSID come from the same subnet?
When on the LAN the user authenticates via AD and the SSID will be setup to use 802.1x with a Radius server and the same AD server.
Whatever the answer would this be the same the other way round?
You can't really get seamless wired to wireless roaming.
You have a wired NIC, connected to the wired network, and it gets one IP address.
You have a wireless NIC, connected to the WiFi, and it also gets an IP address, potentially from the same subnet as the wired adaptor.
If your machine has an open TCP connection from its wired IP address and you unplug the wired cable, those connections will drop, as the NIC with that IP address is now offline. Lots of applications will re-connect, but there are no guarantees.