Mearls talked about 5e PHB sales a bit, which I found interesting. No numbers, but he said the game did well out of the gate in 2014. In 2015, there was a 10% drop off, which they were pleasantly surprised by, since the expected drop off was 50%. Then 2016 sold more than 2014, 2017 sold more than 2016, and 2018 sold more than 2017. This was unheard of; you had to go back to 1e, and its delayed explosion after the Egbert case brought them undreamed of publicity.
Then the pandemic in 2020 caused an industry-wide boom, as everyone’s sales skyrocketed.
On the design front, I was both happy and disappointed. Disappointed because I heavily followed development of 5e in 2012-2014, and there wasn’t anything particularly new said. But at the same time happy because there weren’t any scandalous revelations. Even though Mearls and Rodney Thompson are no longer part of WotC and don’t have to toe a company line, they gave the same goals and design philosophy as they did back during the playtest: not a direct reaction against 4e, but just striving to make complexity something you can opt-in or opt-out of, and let the playtest guide them for class design.
I was really glad they got Rodney Thompson for this, because he’s great at articulating design goals and decisions.