My concern is that there is little room for error with geometric growth.  Lets say that things are happily humming along with bandwidth and block size both increasing by 50% per year.  Then a decade goes by where bandwidth only increases by 30% per year.  In that decade block size grew to 5767% while bandwith grew to 1379%.  So now peoples connections are only 24% as capable of handling the blockchain.

Not a big deal?  Well, except that we can expect the power of nodes to follow some sort of curve ("exponential" in the vernacular) such that most nodes are barely above the threshold to be viable.  Meaning that this event would mean that the majority of nodes would shut down, likely permanently.