I'm sure they are.. the real question is will there ever be upgradeability again, and how fast will spells between refreshes be?
The time is right now especially given the age and non-expandability of the Mac Pro.
This time around, Apple didn't build the the tower nearly everyone in this market would have bought instead of the trash can.
The lack of expandability makes it feel like a doomed purchase, and costing more than $2,000 means spending on something that might prove obsolete in a year (or possibly less) feels extremely frivolous.
Extensible hardware allows us to rationalize a big purchase with the mindset that there's an intent to future-proof with an investment that allocates room for growth.
That concept does not exist with the Mac Pro form factor at all. The purchase is not even slightly user-servicable. Only a subscription to a service/maintenance agreement (read: applecare) provides nigh-full-replacement insurance. And basically, you're just paying for the privilege to gamble. You'll never get to change your old toy into a new toy.
I could definitely see why professionals or otherwise demanding users might prefer internal disks over external ones.
http://www.apple.com/imac/performance/
an alternative to the garden variety external SSD would be an external PCI-E card housing (e.g. sonnet or akitio) connected through a Thunderbolt cable. now that's a lot faster.
but, for that we buy an external housing in addition to the actual storage that goes into the housing. so this is more expensive than computers which let us install a PCI-E storage card directly inside the case. which Macs don't let us do easily or at all.
I actually upgraded my mid 2010 iMac to a 512GB solid state disk. Made soooooo much of a difference. Literally went from almost unuseable to back to my daily workhorse. I can't remember how much time from power-on to login screen was with the original drive, but ballpark a handful of minutes. Now with the new SSD it takes less than 10 seconds.