I don't have a way to test right now, but I am pretty sure you cannot load a version 5 config into a version 6 device. There are a number of formating changes that occur during the upgrade process from 5 to 6.
If you could upgrade the existing device from 5 to 6 then you could migrate the configuration by export/import.
You can rollback the upgrade. So if you can schedule some downtime to upgrade the existing 2050 to grab the updated configuration then rollback to keep production the same.
But if you are worried about potential issues with the upgrade, I feel like upgrading in place on the 2050 and running for a week is your better option anyway. This way you only change on variable at a time instead of upgrading both the OS and hardware together. This way you can be sure of the source of any issues.
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