I would expect the X1 and other E series models to continue to get iDrive updates but they may be more minor in scope and simply not have some of the functionality of the new Nav system. It looks like the X1 won't get the new Nav until the next generation X1 comes out in about 2015. It should be interesting how well that X1 rides in comparsion since that X1 will be based upon a FWD platform with AWD added to it.
Frankly the new Nav system appears nice but it doesn't appear to be a huge upgrade in actual usage vs. perhaps the move from a DVD system to a hard drive based maps. In a few years, it would be nice if they moved to SSD drives instead of hard drives.