What's next for Viacom after Redstone shakeup?

Viacom names Philippe Dauman Chairman
Who will run Viacom?
Sumner Redstone resigns as CBS executive chairman
Statement from Shari Redstone on father

The impact of Sumner Redstone's sudden resignation as CBS executive chairman was ameliorated by news that CEO Les Moonves would take the reins. But the path forward for Viacom, the other jewel of Redstone's media empire, remains much more uncertain, company watchers said.

Viacom, which owns cable networks MTV, Nickelodeon and Comedy Central, followed CBS' lead and replaced the 92-year-old Redstone on Thursday. CEO Philippe Dauman will take over as the company's executive chairman.

While Dauman has bought himself some time, he will likely need to show progress in growing digital, mobile and television businesses either organically or through acquisitions, said Gamco Investors' Mario Gabelli, who owns the second-most Viacom voting shares.

"You have a company with an interesting scale in the entertainment business that could be viewed as up for play in a variety of ways," Gabelli said on CNBC's "Fast Money: Halftime Report."

Leslie Moonves, CEO of CBS Corporation
Redstone resigns as CBS chairman; Viacom to replace as well
Sumner Redstone in 2012
Trading media stocks on CBS changes

The leadership changes come amid a tumultuous time for both Redstone and Viacom. Late last month a California judge ruled Redstone should be subject to a mental competency exam requested by his ex-girlfriend, amid an ongoing dispute about whether he was fit to remain chairman of the companies he controls.

Viacom shares, meanwhile, have fallen more than 30 percent in the last year, lagging many peers in the media sector. The shift to streaming television platforms from cable continues, and Gabelli said capturing noncable audiences should be a priority for Viacom.

Another Viacom investor told CNBC on Thursday that Dauman's performance as chief executive did not warrant the executive chairman appointment.

"We don't think Philippe has done a good job as the CEO," said Eric Jackson, managing director at SpringOwl Asset Management.

In an interview on "Fast Money: Halftime Report," he also stressed the importance of Viacom improving and growing digital platforms. However, doing so through acquisitions would have its challenges, Nomura analyst Anthony DiClemente said earlier Thursday, before the Viacom announcement was made.

It could be difficult to find a buyer for assets of Viacom, which faces structural headwinds, such as falling cable TV ratings and a crowded field of networks. Viacom could potentially become a buyer itself if it deems an acquisition will bolster its position in an ongoing contract renewal dispute with Dish Network, DiClemente added.

"Anything that happens from an M&A perspective has to be approved by the boards of directors of those companies. The trust cannot force M&A on either of these companies," he said.

Disclosure: Nomura provides investment banking services to CBS and has a significant nonequity financial interest in the company.