As you may have read in our Exchange Server 2007 and Windows Server 2008 blog post, the RTM version of Exchange 2007 cannot be installed on Windows Server 2008, but Exchange 2007 Service Pack 1 (SP1)...
Updated Jul 01, 2019
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Mission Impossible: In-Place Upgrading Microsoft Exchange Server 2007 from Windows Server 2003 to Windows Server 2008
I think the same for MS Exchange 2010 in DAG setup, it will require to add a new servers with new OS support exchange 2010 setup to be adding to the existing exchange farm, then remove the old nodes with unsupported OS version.