1.挖矿难度增加，没枚bitcoin对应的价格也在增加
2.挖矿难度增加，收益减少，矿工离开（This is less likely though, because no matter how much they earn, they'll keep their PC running anyway）=>难度降低或保持，收益增加 => 矿工数量最终稳定在一个平衡点