User blog comment:Spawny0908/Rockstar Announces Fan Appreciation Red Dead DLC (and it's FREE!!!)/@comment-82.39.205.139-20110619122209/@comment-3455248-20110619170453

Everything is just a rumor or wishful thinking until Rockstar announces something officially (which they haven't yet). But, yes, a lot of people agree with the three new hideouts you listed. I don't know about Solomon's Folly since it's already on PS3 and there are a number of challenges that include that hideout - if added to XBL it would be tough to retroactively add the challenges.