Intel probably won't bother making a big deal about Ivy Bridge E, if they release it it'll just be to make cheaper eight core CPU's. If you think it's obsolete just don't buy it, people spending that kind of money should make educated choices. As for making the mainstream systems attractive I don't see an issue with this, you don't need to gimp mainstream to provoke high end sales, Intel chips are selling well on both fronts. On the subject of socket changes, Intel have been bring a lot more subsystem changes per generation so when you upgrade it's not just a faster chip.
As for the mobile market, when it comes to a fight against ARM, for a company that makes desktop chips Intel aren't doing too badly. ARM has a lot of advantages as far as manufacturers are concerned as they can just buy the design and build whatever they want around it. Intel aren't really going to follow this lead so it will always be an uphill struggle, to insure a sale, Intel has to make a chip and subsystem that can't be beaten on performance by almost everyone that has made an ARM based SOC. So I think it's brave for them to step into the market, but unless they can create a huge advantage it won't be theirs soon.