Although SSD technology is top of the line and would be great for gaming, it just isn't going to happen anytime soon. Its waaaaaay too expensive atm.
A 100GB SSD costs around £100 if you manage to get yourself a good deal. MS could get that maybe for say half price, so £50 for a 100GB drive for a console. Now take into consideration every game would have to come in a SSD cart and games this gen are on average about 10GB each in size with higher end graphical games like Uncharted take almost full bluray discs with are 50GB. Next gen 50GB will probably become a baseline for the amount of space games need due to improved graphics, physics, etc, with high end games taking even more space. Now for each game, MS would have to pay £25 just for the drive it comes in, now that is ridiculous how you look at it. If you are talking downloadable games, your 100GB drive would only hold approximately 2 games. You would need a 1TB solid state drive next gen for the downloadable option, and I wouldn't want to think how much a 1TB SSD hard drive costs.
So its more likely they will go for SD card technology, as they are a step up from bluray and pretty cheap commercially.
