As per compatibility matrix of Spectrum -Sd integration, spectrum 9.4 could be integrated with SD 12.7 where it is End Of Support by Service desk Team.
We are not getting support in case of any issues in integration. could you all please look into this and provide a fix rather than upgrade of product.
As you mentioned Service Desk Manager 12.7 is now at it's end of support as of December 2015. In theory it may be possible for the integration may work just fine since it's communicating through basic web services. Are you running into a particular problem currently?
The fact is, though, that the best long term solution is to make sure your environment is running Supported releases.