The only people with the right to QQ a bit are the Blood DPS dks's. All Frost or Unholy tanks will find bits of their talents condensed into the blood tree, so if you liked tanking Frost, you'll still have your toys in Cata. Probably not the dualwield but.. cmon, wtf tanking is that with 2 weapons? It doesn't even sound menacing enoug.
And probably they will let sub-speccing into DW in case you choose points from frost as subspec, so tanks will be able to be DW blood too, probably. Or whatever...