Add one more group to the "extended extension" period list...

In addition to several states bumping their enrollment deadlines out until 4/30, and Nevada going even further by bumping theirs out to the end of May, Native Americans / SHOP / Medicaid not having any enrollment deadline at all and of course the "Qualifying Life Events" factor (marriages, divorces, births, adoptions, etc), it turns out there's Yet Another Group which has been given an extention by when they have to enroll in a QHP or Medicaid plan: Those in the ACA's temporary "High-Risk Pool", who were originally supposed to have enrolled by the end of 2013, then the end of April; they've now been given until the end of June to do so:

On Thursday, the Obama administration announced another special enrollment period to extend enrollment in the Affordable Care Act's insurance exchanges, this time for people enrolled in the Pre-Existing Condition Insurance Plan, The Hill's "Healthwatch" reports (Viebeck, "Healthwatch," The Hill, 4/24).

...PCIP was designed to help U.S. residents with serious illnesses gain coverage ahead of January 2014, when the ACA's ban on denying individuals coverage because of pre-existing conditions took effect. The program originally was scheduled to end on Dec. 31, 2013 (California Healthline, 1/15). After several extensions to the program, the Obama administration extended the program for the final time, through April 30 (Millman, "Wonkblog," Washington Post, 4/18).

...According to the announcement, individuals covered under PCIP will have until June 30 to enroll in coverage through HealthCare.gov. The bulletin noted that state-run exchanges would also allow for "a similar special enrollment period." Federal officials said that any PCIP patient who enrolls in an exchange plan by the June 30 deadline will have coverage that is retroactive to May 1.

According to "Healthwatch," the moves likely will affect insurers selling plans through the exchanges because the extension will allow more sick individuals into the risk pool. However, the administration said that the extension was necessary to allow the country's most vulnerable patients more flexibility under the new system ("Healthwatch," The Hill, 4/24).

Not sure how many people are still in this category, but it's worth noting for completeness' sake.