What does the Federal Reserve intend to do with bonds it has purchased under QE?
The leverage ratio, as always, is a ratio between liabilities and equity. It has really no significance, as the liabilities of the Fed, which are mostly dollars, need not to ever be paid back.

Only in the case of inflation would the Fed need to reduce its balance sheet (i.e., sell the public debt or MBS). Do note that the profit of the Fed goes back to the government, thus the debt that is sitting there is an asset and liability of the government at the same time, canceling out. That is, the net debt decreases as the Fed buys bonds from the market. You may also view it as inflation or a money tax that pays back the debt.