Dan knátti fregna:

> One more question: Are there any English translations that have been done by
> native Icelandic speakers? If not, why not?

Not (to my knowledge) of the entire corpus - but surely of individual poems.
Here's a thorough and accurate treatment of Hymiskviða by an Icelandic classicist:

http://www.hi.is/~eybjorn/ugm/hymir/hymis.html

I understand Sigurður Nordal's book on Völuspá is available in English.
I haven't seen the translation but the original has a lot to recommend it.

Kveðja,
Haukur