Legends of Runeterra's Design Director, Andrew Yip, has confirmed the team is not yet committed to delivering a spectator mode.
Yip does mention that although they haven't yet committed to the spectator experience, they understand players put plenty of value in the feature. Runeterra rival and big kid on the block, Hearthstone, received its spectator mode over a year after it initially hit beta, releasing alongside the first large card expansion, Goblins vs Gnomes in December of 2014.
Although spectator mode would be a great feature, it definitely is not a requirement early on and we'll let Riot work on the core game more before we push them too far on that; Something they've been working quite a bit on.
Hi @RiotUmbrage, wanted to know if there is any prediction of a spectator mode on LOR?
No firm commitments on spectator atm; obviously on the list of features we believe players will value though