Eh. I still feel like intel will shuffle most desktop users to the enthusiast platform beginning with Haswell-E. That's not necessarily a bad thing. Octo core CPUs will be the new baseline for that platform along with other goodies - DDR4 and SATA-E.
Normal joe consumer doesn't buy a desktop, this is obvious - but for existing enthusiasts and PC gamers, that niche of a market isn't really declining either. There's still money to be made there and i'm sure intel will create chips for it, even if the progress is slowed. PC gamers tend to spend a lot of money in the ecosystem, even if the "average user" doesn't buy a desktop PC anymore. As mentioned earlier I believe intel will move most of these users to an E platform which isn't necessarily bad.
For absolute huge majority of desktop users, even for majority of gamers. Intel Extreme is WAY too expensive.
If Extreme is only desktop left, then I won't have Intel desktop anymore. I know many people who have desktops and still uppgrade / replace them every now and then and no single one of them have Intel Extreme and no even a signle person would be willing to spend that kind of money for it.
Remember most desktop gamers are not people who go for Intel E & GTX 780 / Titans or SLI setups.
Most spend for whole unit (case, motherboard, memory, GPU, etc) less than price of i7 Extreme chip itself.
Even on enthusiast forums like this one and on pure PC gaming forums Intel Extreme is very rare.