Billionaire investor Dan Loeb's Third Point is taking a "wait-and-see approach" after Sony on Monday evening rejected its plan to spin off the company's entertainment business.
(Read More: Sony rejects Dan Loeb's spin off proposal)
The hedge fund with a 7 percent stake in Sony remains highly engaged and is leaving all options on the table, a source told CNBC. Even a proxy fight has not been ruled out, although it is not seen as likely given Sony's recent progress and commitment to improving its entertainment unit.
Third Point expects Sony to lay out a plan shortly to achieve better profitability in entertainment, and took credit for recent improvements, saying the pressure it has put on the company is a "win-win" for shareholders, sources said.
Sony said in its rejection of the spin-off plan that it believes owning 100 percent of the entertainment division is fundamental to the company's success. The company's U.S.-traded shares fell 5 percent Tuesday.
Loeb's activist hedge fund publicly scorned the entertainment division's performance as recently as last weeek, calling its underperforming summer movies the "Waterworld" and "Ishtar" of 2013.
Movie star George Clooney has swung back, saying Loeb "knows nothing about our business."
(Read More: George Clooney rebuts Loeb's critique of Sony)