I wasn't aware that Sega was even doing that badly lately, financially speaking. If it weren't for a rough patch with Sonic Forces and Valkyria Revolution, I don't think that the quality of their software has really been poor lately either. I've said this in a few places, but if I were Sega I'd have gotten rid of Takashi Iizuka years ago. Terrible director, and a bad designer too, going back to the Carnival Night Zone barrel days. Mania proved that there are a LOT of people out there who can do a better job with the franchise than he and his team have done. Outside of Sonic, the only poorly-received game that Sega's put out for a long while was Revolution, and they didn't develop that game themselves.
Outside of Sonic Team's output, when Sega develops their own games, they're a good developer. You look at their worst games as of late, and they're by and large games they farmed out to less talented studios (like Valkyria Revolution and, even worse, Sonic Boom). I know they're not the same company as they were before the Sammy buyout, but there seems to be a great deal of talent remaining at Sega (as evidenced by Yakuza, Puyo Puyo, and Hatsune Miku) undone by a lack of confidence in either the market or themselves.
If I were King President of Sega, I'd A.) focus on handheld development for the time-being; the console space is dominated by huge dollars that Sega doesn't have and a western-centric culture, and the wild-west mobile market makes new ideas too much of a gamble, B.) divide the Puyo Puyo / PSO developers out of Sonic Team and retool the Sonic staff completely -- you can make excuses for that team all day, but it's clear that there are other people out there who can do this better than they can, C.) take cues from Platinum Games as a developer (you can't have a hit if you don't do everything you can to stand out) and from Nintendo's logic as a publisher during the Nintendo DS days -- quality, quantity, and creativity rules supreme.
As much as I love NiGHTS into Dreams..., Skies of Arcadia, Jet Set Radio, Streets of Rage, Panzer Dragoon, Shining Force, Virtua Fighter, and Shinobi, the most important thing is to be interesting and stay in the public consciousness, whether it's with a nostalgic product or a brand new one.
They don't need Disney now. That's just going to drive this culture of trying to pump out two blockbusters a year. Sega should be spending less money, being more creative, and building a fanbase that's always willing to pay the price for the next game just to see what's next; I think the Disney culture would just complicate things and slow their production down even further with the expectation that they have to create a mega-hit (look how that worked out with Disney Universe). If anything, they haven't needed a merger/buyout from anyone other than maybe Bandai in '97, and ANYONE but Sammy in '04.