We appreciate your feedback.
The DD+ to DD transcode is a feature we are considering for the Roku-4 but don't have a specific update to share at this time. The Roku-4 hardware will not need to change to add the DD+ to DD transcode capability.
Dolby Digital(DD) and DTS audio streams are already supported via pass-thru to both the HDMI and optical connector.
DD+ is also supported via pass-thru to HDMI, and in some cases it can be sent over the SPDIF optical connector to a receiver that is able to accept the DD+ stream.
Creating a firmware update to transcode Dolby Digital Plus to plain Dolby Digital would not only validate Roku's decision to include the optical port in the first place, but also create a fantastic differentiation feature that would further set the Roku-4 apart from its competitors. I also requested this feature in the following thread:
Feature Requests - 4th Quarter 2015