Unless I missed something, the estate is the default beneficiary.   
if you have not already done a lump sum distribution, you still have avenues to potentially reduce tax liability to the beneficiaries of the estate.

1) was there a will?  
2) irs does not prohibit an estate to hold an estate inherited IRA.  If the custodian is willing, a trustee to trustee transfer to an estate of xyz inherited IRA can be done.  In most cases IRA custodian will not take the risk without a private letter ruling from IRS legal counsel to do a trustee to trustee transfer to the beneficiaries from either directly from the decedent’s Ira account to the beneficiaries or from estate inherited Ira to the beneficiaries.  
3). I believe current rules require a an estate inherited IRA to be fully distributed in 5 years. (Verify against current IRS regulations).   
4). Downside is the estate would remain open during the distribution period. 

4).  Downside is the estate would remain 

If this option is available, it could reduce the tax liability to the beneficiaries of the estate.   

Note, this does not apply to a 401k, rules for trustee to trustee transfer are defined in the 401k plan document.   Nasty place to leave qualified funds in an employer sponsored 401k plan.  Leaving funds in a employer sponsored qualified account can have significant tax implications to non spouse beneficiaries.