Disney apparently wants to continue the theme of releasing Star Wars movies around Christmas.
The stand-alone Han Solo Star Wars spin-off movie is currently due to release in May, 2018. But, a report from Making Star Wars suggests that this date has been pushed back to December of the same year. The reason? Both Episode VII and Rogue One were released in December, which contributed to their success.
MSW's sources claim that December 13th, 2018, will be the new date for Star Wars: Han Solo. It does admit that the date is subject to change.
Last January, Disney shifted Star Wars: Episode VIII from May to December 2017, so it would make sense to do the same thing for Han Solo. Rogue One just recently surpassed Captain America: Civil War to secure its place as the second highest-grossing movie of 2016.
Source: Making Star Wars