Song joined the Hammers from Barcelona in the summer transfer window and has made an immediate impact in their first-team squad.
He has brought a presence to the midfield, but it is his technical ability which has really stood-out and helped West Ham dictate the play during their matches so far this season.
He has been a key reason behind Sam Allardyce's men's success to date, which has lifted them into fifth position in the Premier League table.
It appears that his impact has not gone unnoticed by the Hammers hierarchy, either, and Sullivan revealed that he is hoping to do a deal with Barcelona for the central-midfielder, but he knows it could be a tough transfer to pull off.
"Could he [Song] leave at the end of the season? Yes he could - loan players always can," Sullivan told Sky Sports News.
"Barcelona paid £15m for him. You have to judge him over the season and I think Song has to judge West Ham over the season.
"He loves England and his family loves London. We hope that we can conclude a deal to sign him but if we can't, we can't."
If West Ham can break into Europe, as they are aiming, that should help convince Song to stay at the Boleyn Ground. The Cameroonian has enjoyed a glistening career at the top of the game and to move to a team without the potential to play in European competition would be a step-down.
However, his time at Barcelona was a major disappointment and he seems to be thriving with a fan-base supporting him once again.
Song will next be in action this weekend when West Ham take on Aston Villa and seek another three points to help consolidate their lofty position in the table.