I believe that this is still valid (David will re-confirm for sure)
MQTTv1 will continue to use the “old” ConfigAdmin PID: org.openhab.mqtt and it’s own bundle names (org.openhab.binding.mqtt & org.openhab.io.transport.mqtt)
For MQTTv2 binding: PID: org.eclipse.mqtt and the bundles are: org.eclipse.smarthome.binding.mqtt & org.eclipse.smarthome.io.transport.mqtt & org.eclipse.paho.client.mqttv3)
You can test this theory in a demo system by installing both addons and putting some basic configs.
I used M8 and they work fine in parallel.