After a number of technical issues relating to RAIDs over the last week or so, Niantic has decided to extend the time Ho-Oh will appear in RAIDs.
This is first brought to light by Reddit user okkthxbye, who had posted a screenshot of an email he received from the Pokemon GO team apologizing for the issues, and stating the Ho-Oh time extension.
This is later confirmed elsewhere on the site by NianticGeorge, Reddit’s resident Niantic Support Representative.
Some believe that this extension means that the introduction of 3rd generation Pokemon will also be pushed back, though most are just happy to have more time to catch the legendary bird. Ho-Oh was originally going to disappear on December 12. They have not stated when the new deadline will be, though i am sure we will find out in the coming weeks