I don’t think we should read too much into his tweets or articles. He mostly likely will (and should) submit his name to the draft and get feedback from the NBA Advisory Board. Once he has that info, he will make the decision he feels is best for him.
If I had to guess, I would say he has no idea about what he is going to do right now and he wrote an article that could be interpreted as a farewell because he was reflecting on the glory of last weekend. He didn’t mention next year, because the article wasn’t about next year.