I wouldn't agree to a merger. Partnership, as what they've done with the laptops, absolutely. I'll entertain this thought a little more...
With the branded laptops, can you imagine the resources SEGA would have for their Arcade division? Upgraded models of RingWide to compete with TAITO's NESiCA network service? Possibly worldwide releases of SEGA's special edition gaming laptops to help push their own service of games, much like Sega used to have of their online games service they had for awhile before it was hacked and brought down? Toshiba would have server farms.. I wouldn't see how they couldn't let SEGA buy up some to house their network on and further establish the possibilities of a worldwide SEGA network to rival NESiCA.
As for home consoles, I doubt Toshiba would venture into something outside of TVs, BluRay Players, camcorders, and PCs. IF they were to even think about something like that, it would be more akin to a home entertainment computer that would have a BluRay drive and access to SEGA's Online service, that would have a large backlog of all their games they currently have available on Steam with a SEGA dedicated service. Would be killer if they then threw on online games, such as VF5:FS. However, they've already brought that game to the current home consoles, so it would need to be more exclusive and newer games.
Honestly, I'd love for SEGA to bring back their dedicated online SEGA service in some form or another. Classic and newer SEGA games, available for a small, monthly/yearly fee. Free updates/patches. Possibly include their mobile games as well and special incentives for members, such as give-aways, or the ability to purchase SEGA branded merchandise.
But why put such effort into that when SEGA also has quite a good footing with Steam? So, with that in mind, it pretty much negates any of my thoughts. Outside of the special edition laptops, and the possibility of leveraging Toshiba's PC resources for their arcades, there's not much else there.