... that's not true. The Fed's balance sheet, from a transaction basis, topped $3 trillion some 5-6 weeks ago. The only reason the Fed reported a $3 trillion number in today's H.4.1 , or $3.013,333 trillion to be precise, is because all those MBS purchased in September and October following the September 13 reactivation of QE4EVA finally settled. In reality, the Fed's balance sheet is now some $3.12 trillion as there is about a $80-$120 billion lag between what the Fed has actually purchased, and what has settled. Luckily, at least Treasury purchases take far less to settle.
None of the above should come as a surprise to anyone: the Fed's balance sheet has been, even purely nominally, at $2.8/2.9 trillion for months. Wake us up when the Fed's balance sheet is $4 trillion, in precisely 11 months.