Should it be merged or migrated here someday, because I found similar questions there.
Good question - it's actually been addressed on meta.stackoverflow.com in several questions.
The bottom line is that old questions are never migrated1 and new questions are only migrated if they are off-topic on the first site.
With that said, it's quite likely that a pure chess question would get better answers here than on board and card games, so depending on the question, it could be migrated shortly after being asked. However, there have been only 6 questions asked on board and card games in the last year. Of those, only one or two would have really been on-topic here. Stack Exchange is fairly self-policing - most users find the correct site for their questions.
: When a site first graduates from beta it's possible to do a one-time batch migration of questions from stackoverflow.com and ostensibly from other Stack Exchange sites as applicable. Chess.SE is a ways away from graduating, and the questions on boardgames.SE are on topic there already, so they will almost certainly remain there.