Tax Notes ($) reports that the President's new budget calls for a restoration of the 2009 estate tax regime in 2013, when the December compromise expires. That means, at a minimum, that the exempt amount falls back to $3.5 million. It could also mean the end of spousal portability of the estate tax exemption.
But in the Byzantine logic of Congressional scoring, this tax increase is scored as a tax cut! It would replace the reversion to the even lower $1 million exemption.