The real problem is the inevitable centralization of mining.
Year after year, the number of active mining pools go up.
Year after year, concern trolls talk about the "inevitable centralization" of mining.
And year after year the bitcoin faithful bury their head in the sand, "if we don't worry about it, it is not a problem".
I have wondered if several decades from now, governments might not end up securing the blockchain by goverment-funded mining in order to protect the economy, property records etc. from evil 51% attacks by other nations or terrorist groups. I might be dreaming of unicorns and rainbows though....