I presume that you mean block level access over wifi? Surely iSCSI already works over WiFi, if a little slowly. Why would you want to do this in preference to accessing files using NFS or HTTP?
Although if you had a stupidly fast internet connection it would be possible to hold devices images in RAM centrally and may turn out to be quicker than booting from local storage.
One reason why it's a clear cut no: latency. Maybe for file servers but not for operating system and application files. Expect always to have a few GBs accessible by wire (even if one day it is included in the SOC).
Form that viewpoint, I can see a laptop disk drive that only needs a power connection. Battery-operated, you could even keep it in your bag while using it,
Big questions, however, are a) whether people will still want external drives for thei laptops. SSDs and the cloud may supplant them, b) whether the bandwidth is reliable enough (what if I sit next to someone who also has a Wi-Fi external drive?) and c) whether it is a wise idea to make it so easy to detach your disk. Software will have to be prepared to handle the case "user picks up laptop and walks out of range of external disk"
Especially for reasons a and b, I do not see this happen.
I don't know the latency of SATA off the top of my head, but I would assume it would be less then that of Wi-Fi. With the way the OS currently controls hard drives, this proposal probably just won't work. Since this pretty much rules out an OS drive over Wi-Fi (lots of random reads), we could instead think of a NAS setup for mass storage. So we have a small NAS with Wi-Fi, with samba or NFS protocols, and use it as a storage drive.
Personally though, I don't mind having an internal SSD in my laptop (although it is a bit small, really should get a bigger one). I also don't mind cables for external storage drives. As for Wi-Fi, I usually have a hard time hitting the maximum bandwidth of my AP (where maximum bandwidth is slightly less then half the connection speed). Wi-Fi is also prone to interference. One interesting thing about the 802.11 ac spec is that it now supports channel bonding on upto eight channels, which severely limits the 5GHz band, which was supposed to take away all the congestion we have on 2.4GHz.
Always no, often yes. Just think about copying about anything from/to HDD. Now let it take ten times as long. Game installations, torrents, everything. Currently HDD is often a bottleneck.
Yeah, DMA makes it "not that bad" at first glance, but it's just a workaround (hdd to hdd) and you'll see that you need a workaround on workaround next to a workaround when you go that alley, instead of just getting just bandwidth.
Although if you had a stupidly fast internet connection it would be possible to hold devices images in RAM centrally and may turn out to be quicker than booting from local storage.