Thursday night's speech would be a good time for the President to announce a new filing deadline for everyone of June 15.  Tomorrow morning's White House press conference would be even better. 

What's significant about your question is that you mention IRS twice and state ncome tax not at all,.  Are you fortunate enough to live in a state with no income tax, or one that has already decided not to tax unemployment?  

My guess is two weeks for IRS to issue a worksheet for computing the exclusion and change its programs for processing e-filed and paper returns.  Remember how they waited until February 12, to make sure they had all the changes from the December 27 law?  Then another two weeks for Intuit and other software developers to change heir programs.  But state revenue departments may need two or three months, whether or not they conform.