I believe Firewire is here to stay for quite awhile (I'm talking several years), in place of yes even USB 3 and Thunderbolt -- here's why I think that:

1.  If you visit Avid or Apple Logic support forums you see a lot of posts as to why USB 2's method of data transfer vs. Firewire's method creates several advantages in FW's favor when recording high track counts or high i/o (for bouncing tracks through outboard summing boxes or other analog gear).   Sure USB 3 looks good - but bear in mind many computers (even recent Macs) out there are still USB2 & FW400 -- those folks will choose FW since FW interfaces need virtually no involvement from the CPU to move data (hence less clipping and/or better ext recording drive performance) compared to USB.  Avid doesn't even support using USB drives for recording, there's a reason for that.
   (Note: I'm NOT saying USB as an interface is "inferior" to Firewire at all, just that FW 400/800's methods of moving data bend it toward high i/o counts for recording over most pre USB 3 -- especially when it comes to drive storage.  People who buy FW drives will often daisy chain up to a FW interface.)

2. FW800 is still the "non PCI Express card" big dog for high density i/o for audio interfaces over new standards like LightPeak/Thunderbolt -- why?  LP/Thunderbolt is literally so dang new/fresh that the only thing that we'll soon see early on will be ultra-fast HD storage.  Interfaces will come, yes, but in the meantime FW400/800 is probably your most popular non PCI-X way to a high-density interface.

I really like the features of the UFX -- bear in mind I'm sure once LightPeak/TBolt take off RME will be there.    But SoS just handed FF800 their 2011 Interface of the year -- no eSata or Thunderbolt technologies are even on the horizon yet.   I think FW is a market RME and others will be happy to build FW-capable gear for a Loonnnnnnng time to come.