Every president has had an official portrait painted. In fact each president has had two more or less official portraits painted: the official official one at the White House and another at the Smithsonian.
The reason why there isn't going to be an unveiling at the White House is probably because neither Trump nor Obama really wanted one, and each man knows it. I suppose they are both okay with that, though neither is ever going to be happy about anything having to do with the other.
Besides, when odingo was in office, there were pictures of him all over the White House. Some lib columnist remarked that it creeped him out at the enormous number of pictures of obama that were on the walls.
That news never hit the mainstream.