It is possible that Xemnas may had access unconsiously to some of Master Eraqus's memories...as it was he who told Aqua about the mechanism (that is not the only secret knowledge a true keyblade master gets to know though, there was just not shown more in BBS).
Eraqus's heart is part of the whole Xehanort/Terra/Eraqus-mess that Apprentice Xehanort was because his heart is hiding inside Terra's.
The chamber of Repose can be accessed if one knows the program and the password to it in Radiant Garden's computer though...so Sora and Riku may get access to it in DDD or early in KH III.
The question would however be if Ven's heart would be able to even fully "interact" with Sora...we don't know how severe Ven's injuries still are and if his heart can be "awakened" within Sora without causing harm to both of them in the process.
Eraqus's heart is part of the whole Xehanort/Terra/Eraqus-mess that Apprentice Xehanort was because his heart is hiding inside Terra's.
The chamber of Repose can be accessed if one knows the program and the password to it in Radiant Garden's computer though...so Sora and Riku may get access to it in DDD or early in KH III.
The question would however be if Ven's heart would be able to even fully "interact" with Sora...we don't know how severe Ven's injuries still are and if his heart can be "awakened" within Sora without causing harm to both of them in the process.