Not really. Most users will only have a 2.0 setup and that's who Google is aiming their device for - the average person who will use an app or chromecast or other streaming box hooked to their tv. The streaming box replaces their cable box. Things like AVRs are rare, and most sound bars are just fancier 2.0 systems. Plus you can use the same stream for mobile and tablet users who don't have more than stereo anyways.
People who wanted 5.1 would either get the episodes as a subscription to the program (you can still get downloaded tv shows). Or provided as a non live tv streaming service like amazon prime, netflix, Disney+ etc where there is no real time 5.1 encoding requirement.