Hell, I'd buy it. Day 1.
But seriously. While I've gone on to basically anex Sony's consoles into the role that Sega's used to own (road dawgs with my Nintendo ones), it's just not been the same.
So, I would definitely love to see Sega's triumphant return to the market. With new and exciting development teams like Platinum Games on their side, as well as always reliable staff, such as AM2 and the dudes behind the likes of Ryu Ga Gotoku and Jet Set Radio, they could definitely make a compelling case for a solid line-up for 1st party coverage. And I could easily see the likes of Capcom, Arc Systems, Treasure and SNK, at least, sitting and paying attention, if a new (and ESPECIALLY) affordable alternative to the PS3 and 360 was available, while also offering a decidedly different flavor to Nintendo's own. Sega was the undisputed rival to Nintendo back in the day (Sega does what NintenDON'T!
), because Sega had some serious Swagg, back in the day.
My only thing would be, would they be poised to be still relevant, at this point in time? I mean, the main reason the Saturn and Dreamcast failed, was due to some poor marketing decisions on Sega's part. And for all that the DC was, for all sakes and puposes, a competent rival to the PS2, it couldn't make up for the failings of its immediate ancestry. Would Sega laying fallow for about a decade, be enough for people to be willing to trust them again? I'd love to think as such.
If nothing else, having a console that would just be an immediate home equivalent to whatever Sega has in store for the arcade market would be enough to make me happy.