Cisco Press CCNP Voice books from 2011, update any time soon?

So for my work I was thinking about buying a CCNA Voice book for reference, but since I'll be working on my NP Voice after VCP and NP R/S, I figure I might as well just put money towards the NP level voice books.
My question is, I'm probably a year'ish out from studying the CCNP Voice, and wondering if these books are expected to be updated within the next year or so? I see Cisco Press had a release of books in 2008, then 2011, so I'm wondering if since it's been 3 years if these will be updating again soon or if the most recent update was strictly due to changing formats from CCVP to CCNP V.
Again this is for immediate reference material for work, but hoping these will be relevant in the next year or so - Thanks!
My question is, I'm probably a year'ish out from studying the CCNP Voice, and wondering if these books are expected to be updated within the next year or so? I see Cisco Press had a release of books in 2008, then 2011, so I'm wondering if since it's been 3 years if these will be updating again soon or if the most recent update was strictly due to changing formats from CCVP to CCNP V.
Again this is for immediate reference material for work, but hoping these will be relevant in the next year or so - Thanks!
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