The xbox is 10 years old. I've got a few tablets, consoles, laptops and gaming desktops and still use the consoles more than anything, just for convenience. I quit using the PC because of upgrade garb and it's full of online cheats, etc. After 4 months, you can't game online without massive exploits running rampant. I love the PC, but it just doesn't do it for me anymore.
I used my laptop running an NVidia 4200M over HDMI and the graphics were slightly better than the 360, so I'm not sure what you're smoking when you say an iconica with a tegra 2 would outperform it. If it were true, they'd be developing games like BF3 for tablets. As for 1080p, it is true 1080p, but some games drop to a lower resolution to gain framerate. The same goes with AA. The 360 is capable, but they dropped the requirement for it. Even with AA missing from games, it still doesn't have the Jaggies that the PS3 has. They're both still great (I own both), but I get tired of the sharp edges on some of the PS3 games.
I'm not trying to fuel the flames or start an argument with you, as much as just add some input on it. You're still talking about 10 year old technology vs something that's relatively new and more efficient. Regardless of the outcome, it's win/win for us on every end. We'll have cheaper toys and cheaper games, and the big name consoles will have to change their business model to compete, which usually means competitive pricing. The thing we need to worry about the most is whether those companies will pull Apple BS and start scrutinizing patents.
Another thing that may be a plus and minus is whether or not they're going to keep the programming the same across the board. With that many new mini-consoles coming out, they don't want to split up the development and kill each other off because of fragmentation and dilution. I WANT to see these guys succeed because I love games, regardless of the media they're on... BUT, I look for these to be an addition to a gamer's toolbox, rather than a replacement for higher-powered system that allows for larger titles. In that aspect, is IS apples and oranges.
Considering the price, you're not going to see people buy these smaller consoles and just quit there. Like the other guy said, the kids are still going to want the big console... whether it makes sense or not, parents buy what kids want. My kid plays on everything, and I'm currently running a 6400, Wii, WiiU PS1, PS2, PCs, 360, PS3, Genesis and intellivision in one room. They seem to like the 360 better (and my daughter likes her tablet), but there's no doubt in my mind that I'll probably end up buying a few of these things just to fill in the blanks. Will it replace the high end consoles? Doubtful.. but it's more stuff for us to enjoy, and the more that are out there, the cheaper it is.