Yes. FW400 drives are hard to find and FW800 is quite rare and $$$, even in the apple stores.
Rare where? At Bubba's "no diversity, as generic PC as possible" corner store???
Newegg has over a page of them. (listed as 1394b on several )
http://www.newegg.com/Product/Produ...iption=firewire hard drive 800&x=0&y=0&Page=2
OWC has gobs of options
https://eshop.macsales.com/shop/firewire/
If shop somewhere were folks go for performance external storage will find FW800/1394b options. If shopping where folks overwhelmingly go to buy USB external hard drives then probably not. (the latter places tend to stock drives that have interfaces that standard PCs have. Yeah, it is very rare that an off-the-shelf PC will have FW800. Typically need a PCI card to put FW800 on one. )
Would it kill them to give us at least a little upgrade ability -- via expresscard slots or something like it. Of course that's doubtful now that they're vanishing from laptops as well.
PCI cards sometimes also bring additional support issues (need to shutdown to get smooth insert/remove behaviour). Plus it adds to the complexity of the iMac design. The iMac is vertically oriented, low height board. Where does a slot go? Not likely going to have something hanging out of the side; that doesn't seem likely to pass the "steve jobs elegant lines" test. So a door/hole in the back of the case.
It is a bit ironic in that Apple seems to have trouble with eSATA not being a robust plug-n-play solution, but blocking progression on FW. USB 3.0 seems likely to be relatively "not as efficient" as USB 2.0 versus FW when it comes to pushing it at full speed too.
It is a bit of a catch-22. There are no FW3200 chips you can order ( folks did demos but does anyone have a web link to a catalog page which lists where can buy production product offerings for this speed. It can be a standard but if no one is shipping in quantity numbers that is moot. )
No silicon vendor is going to go to production without a huge order and few (who willing to butt heads with Intel) wants to place a larger order. So progression is dead in the water.
At one point there was talk of using FW as simple plug and play interconnect between high end audio/video equipment. It looks like equipment that has any interconnect is going toward Ethernet (e.g., http://www.dlna.org/home ).
The iMac could get by better without PCI additions ( expresscard or PCI) if the I/O options weren't as limited. For example two independent Firewire channels ( so one FW400 device doesn't drop all connections down to FW400.). Or perhaps a being aggressive and adding a PCI discrete USB 3.0 chip to the board ( NEC is shipping a discrete USB 3.0 chip this fall and has been sampling for a while). (which effectively would give two higher speed channels FW800 and USB 3.0). I think that would fit most folks needs for "expansion". Primarily what folks need is either higher storage + external data gathering device connections. (or external RAID connections). There are a few other expansion needs but those are more niche needs.
P.S. The Physical Apple stores have a broader collection of skins/covers of iPods/iPhones than they have of anything Mac accessory oriented.