Not excited at all. The PC is currently a generation ahead of consoles and the newer consoles will only have in them parts probably released in the year succeeded to release year so most like the 600 series Nvidia cards or 6000 series with an i5 2500k or i7 2600k processor. Most likely the i5. The Xbox 360 only used the best parts that came out in 2004 so therefore the newer model will likely do the same.
For those with newer PC's, i.e. 2500K, 2600K owners with Nvidia 570, equivalent or better cards then the improvement won't be that much and there is nothing at all to get excited about honestly.
To be perfectly honest, with MS a massive fan of streaming and cloud based systems I expect an online type of download system where you download and save games as 'apps' to the xbox 360. Those with the new 360 dashboard will be aware of the app market now. This in my opinion will cause a massive server problem which will take MS a while to get fully functioning. I mean, xbox live goes down enough as it is without things like that. Its unlikely they'll use BluRay.
I also expect the new xbox to run Windows 8 and be fully compatible with mobiles and pc's as well. This will give them an edge over Sony for compatibility, the same edge Apple has with its compatibility of devices like Macbook's, iPads, iPhones and iPod's. Its that easy syncing that means buyers stick with the same brand as it makes their life easier. Another advantage of this would be that xbox players could play PC gamers at last on cross compatible servers as they'd both be running Windows 8. This would be massive for MS. Essentially, the new xbox would be an entry level budget gaming pc for those who don't want to enter the self build scene.
Its most likely that MS will go with AMD hardware to keep costs down whilst still charging around £400 for the newer system.