In this talk they skip over it fast and it starts around the 31 minute mark.
Mostly the midi implementation will be easier and there will be general higher audio quality.
Boringly enough as the more serious apps already have implemented their own midi solutions (some much better than others!) and some have already gone to the same audio quality...
Well maybe the midi is good news as there is good applications that have inferior midi...
Another thing that seems to be coming but is not mentioned in the video and that I picked up from arstechnica.com is a new USB type-C that will allow for direct connection of USB microphones etc which would be great as there is solutions but they do cost money and involve specific devices and external hardware...
http://arstechnica.com/gadgets/2015/05/android-m-embraces-usb-type-c-midi-devices/
No mention of latency.