Considering Mojang wanted him developer on their team, it looks like he's a good developer. However, I don't think it will become equally as popular and/or more popular than Minecraft, or Terraria for that matter.
I understand why you would think so but so far the game looks like it picks up where Minecraft left off, he basically took out the mining and replaced it with Role playing elements which is what makes it unique and not a Minecraft clone.
You guys seen Cube World?