Is the English translation of "Book of Mormon" ever revised or updated, and if so, on what basis given that the golden plates have disappeared? The English used in the initial translation of the book of Mormon is KJV-esque English. I'm wondering if there have ever been new English translations as time goes by, and as the English language has developed? 

If so, what are these translations based off, considering we no longer have access to the golden plates? Would it just paraphrase the original translation, but in modern English?
No, the Book of Mormon has never been revised into a more modern English dialect.

There have been various updates to the printing of the Book of Mormon over time to correct errors in the typesetting of earlier editions.  The first edition was set and printed in haste, from a manuscript handwritten by Oliver Cowdery under Joseph Smith's dictation.  Cowdery didn't have the clearest of handwriting, leading to the first edition containing thousands of typos, some of them truly bizarre such as rendering "robber" as "nobler", others more understandable, like changing "formation" to "foundation".

Also, the original printing came in 1829, before English spelling had become standardized.  (Noah Webster published his first American English dictionary in 1828, and at the time it was only one of many available, each using wildly varying spellings for many common words.)  Because of these various factors, there have been several times in which new printings of the Book of Mormon have been updated for correctness.  However, the basic narrative, the doctrines taught therein, and the Biblical feel of the language used, have always remained consistent with the original English translation.

Source: Understanding Textual Changes in the Book of Mormon