I'm glad everyone's relieved this isn't planned for the Java edition of Minecraft, but do expect there to be less mods being worked on for the pc version in future. I would expect a lot of mod makers will shift their attention to the paid platform where they can get a little compensation for their work. Think about it, if you were a mod maker spending countless hours modding wouldn't you prefer getting something for your efforts?
I don't plan on shifting platforms with my mods. And as for earning a living off of it I would think it's a pipe dream. Sure, some may hit it big, but by and large not enough money will be made by the average modder. It's like having a dream of being a video game programmer when in high school, and then you finally realize that you need food on the table to survive.
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I second Thermal Expansion. The other to consider is Applied Energistics.