In addition to the Greenbone OS lifecycle we started to publish a lifecycle overview for GSM appliances. As a matter of technical advances, older hardware appliances are not capable of the capacities newer GOS versions require.
The overview informs about which GOS version is supported for the appliances. The latest status will be available here:
The physical appliances GSM 25/100/500/510/550 will not be supported beyond GOS 4.3. However, we just released fresh GOS 4.3 and it is a Long-Term-Support (LTS) release. So, there is plenty of time (approx. 18 month) to plan for an upgrade to a new generation. In combination with a subscription renewal, Greenbone makes special offers to upgrade the hardware already now.