Sony Corp. stock soared today following the news that Chief Executive Kaz Hirai is stepping down from the helm of the Japanese corporation, to be succeeded by Chief Financial Officer Kenichiro Yoshida.

Wall Street observers say the stock movement is a sign of investor speculation that this changing of the guard might open the door to a sale of Sony’s entertainment assets. Sony’s stock closed at $51.99 Friday, rising 6% in the day’s trading at a time when the markets tanked.

However, insiders at the studio say they see no evidence of a shifting corporate strategy under Hirai’s No. 2. Sony will continue to look for opportunities to grow its film and television business, whether through acquisition or merger, sources say. There’s been no discussion of a sale.

Hirai, an executive who got his start at Sony Music and ran Sony’s PlayStation group before claiming the top job in Tokyo, has been a fierce advocate for Sony’s entertainment business.

As recently as last month, Hirai spoke to Bloomberg Television about wanting to be a buyer in the wave of consolidation sweeping through the industry. Though Sony lost out on 21st Century Fox’s film and television assets, he underscored the importance of taking whatever steps were necessary for the company to remain in control of its own fate.

Hirai plans to remain involved in Sony’s entertainment business as chairman, sources said, providing his advice and expertise for this one part of the Tokyo conglomerate’s business where Yoshida lacks experience.

Still, Yoshida is a numbers guy with a more cautious outlook. In an interview with The Wall Street Journal, he said he sees Sony as a technology company — and one that should keep consumer electronics at its core.

Those in the U.S. who know Yoshida describe him as a pragmatic businessman who doesn’t regard any part of Sony’s business as a sacred cow. That’s what has triggered speculation that he might be open to selling — just as former General Electric CEO Jeff Immelt shed the company’s media unit to bring GE back to its industrial core.

Said one industry observer: “Kaz was not interested in selling and Yoshida is really not too keen on the entertainment business so everyone (is speculating) that Sony is ready for a sale.”