No, Diablo IV isn't coming out soon nor is a trailer already available. But, Blizzard did have some good news to share about the upcoming Diablo game.
After dabbling with a pay-to-win mechanic in Diablo 3's Auction House and diving deep with Diablo Immortal, Blizzard just confirmed that fans have no reason to worry that Diablo 4 will have a similar feature. According to the company's latest development update, Diablo IV will launch at full retail price and let players spend money on cosmetics, before assuring players that no one will be "able to pay for power."
In the same lengthy post, Blizzard explained that Diablo 4's post-launch content is structured around Seasons and Battle Passes. This is the same model used by Diablo III. The free progression system lets players earn rewards without paying. Of course, there's a Battle Pass as well. Also, Blizzard doesn't want you to refer to them as Battle Passes. Even if the company described to the system as having a "battle pass-style progression", Blizzard wants you to call it the Season Pass and said it will have "free tiers and premium tiers."