Hi! Welcome to BI.
Nobody really knows whether this site will stay open or not. The owners have not been on in years. This is what we know, though:
-The site domain apparently expires in August, at which point it will need to be renewed.
-Other Insider Sites which have had the actual game close down (ex. Free Realms Insider) are still up and running, just pretty much abandoned.
So there is no definite answer to whether the site will remain open or not, these are just clues that members have gathered. Hope this helps!