Many in the Volkswagen diesel community are fanatical about their fuel economy and are understandably angry that a fix for the current emissions scandal may see them lose fuel economy in order to lower NOx output.
The aftermarket community has provided modifications for the DPF and Adblue systems in the past, meaning there’s good chance they’ll provide parts and tuning to revert any changes Volkswagen may implement on the affected models.
There are a number of paths which Volkswagen may take that range from an ECM patch to new SCR hardware that could be installed.
The non-SCR models may get a software patch that would alter the injection timing and increase the regen cycle. This would cause the NOx emissions to go down but would take fuel economy and power along with it. It could also cause carbon build-up on the pistons and catalyst which could lead to increased maintenance costs for the owners.
The other path for the non-SCR cars is implementation of an SCR system, but that may not be cost effective due to the parts cost and labor required.