Afaik both are already on the todo list, but DVD does NOT exclude additional coding.
For starters DVD resolution is limited to 576/480p. BD goes upto 1080p. So additional code is required to downconvert the resolution. Then you have additional code for the formats. DVD format codec is limited to MPEG2, BD has 3 of them AVC,VC1 and MPEG2. MPEG2 use on a bd isn't very common. Most i've seen use AVC or VC1. Take the above into account, you then have additional code to convert (if needed) from AVC/VC1/MPEG2 to MPEG2.
Then we have the audio codec. DVD is limited to
https://en.wikipedia.org/wiki/DVD-Video#Audio_data Blu-ray has about 2-3x as many official codec types
https://en.wikipedia.org/wiki/Blu-ray#Audio, it crashes. So you have additional code to convert from the BD audio type to the DVD audio type of your choice
and THEN you have to combine those 2. It's not as easy as it sounds.