Diablo 4 will not feature a real-money auction house, according to an interview with Polygon.
Executive Producer Allen Adham stated that a real-money auction house wasn’t something they wanted to return to after Diablo 3, but still want to enable trading between players,
“There are a lot of great elements to trade if it’s done in a contained way. So we’ve got some pretty solid ideas on how to make trade viable without letting it disrupt the game.”
However, as pointed out on a stream with Quin69 (thanks SkillUp), Diablo 4 will include microtransactions. Game director Luis Barriga also spoke on avoiding the server issues which plagued Diablo 3 at launch,
“We were pretty protective of our not showing too much of our content and we had a limited beta during Diablo 3. I think you will see us take a different approach here.”
Long term plans for Diablo 4 include a beta, but we don’t have any concrete details on that at the moment. Finally, content updates were discussed, with Adhman stating,
“We aspire to generate more content at a higher cadence, and so we’re building out the team from the ground up in service of that.”