That's seems to be a long proof to show that future generators purely motivated by profit would modify their clients to jump in & out of the game based on the presence of unserviced transaction fees in the transaction queue, while ignoring transactions that don't meet their own minimum fee, once the block reward drops low enough that it is not enough on it's own.  This is pretty much by design, as that is when we will hit a balanced difficulty level.  Yet, even if there are profit seeking generators that would benefit by stopping and starting, it is unreasonable to assume that there will not be significant generation motivated by rational self interest other than profit.  For example, some future generators might be motivated to maintain a minimum level of security for defense of their own balances; or a future version of a bitcoin credit union might be motivated to process transactions for free.  Even if free transaction generators were selective in who they accept transactions from, they are likely to have agreements with other such institutions to process one anothers' mermbers' transactions.

And if I can think of ways around it now, I'm sure that there will be other forces influencing the pricing when the market actually comes to that point.  This is way to complex to predict.