I've talked about this before on a Jet Set Radio blog I run, but I pretty much share the opinion that Sega has no real business making an in-house Japanese developed game anymore. I've noticed a lot of people are extremely cynical about where Sega is going, but I always make it clear that poor sales= no sequels. There's this one guy in particular that keeps popping up, that I've just taken to ignoring now, that constantly complains Sega isn't doing what he wants, and I keep explaining that it's because of sales, being too risky, and although I've never said it to him, people like him. One particular example I brought up was NiGHTS: Journey of Dreams, and how Sega took a huge gamble on making it at all, especially considering how much bigger it was than the first game. The fact it bombed probably affected Sega's desire to try something like that again (which they haven't, except for arguably Sonic games).
I think the sales and reception Sega got from the immediate post-Dreamcast era, that is, 2002 to around 2007, has REALLY soured any luck of more games in that vein. If people had just bought the games they were making instead of bitching about Sonic and the Dreamcast, we might singing a different tune.