On a whim I decided to do an Amazon search for any SISAS material as that is the exam I'm working on and came across the pre-orders for SENSS and SIMOS.  It looks like the release date is Janurary 2015 for the time being which I find hard to wrap my head around considering that there's no other written material available for this new track.
SIMOS
http://www.amazon.com/Security-SIMOS-300-209-Official-Certification/dp/158714428X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0DAN6Z7R31X3832XAZH6
SENSS
Amazon.com: CCNP Security SENSS 300-206 Official Cert Guide (Certification Guide) (9781587144271): Brandon Anastasoff, Mark Bernard: Books
In any case I've been doing the IPExpert video series on the course for the time being, and I know CBT Nuggets is releasing some videos for the track as well.
I was fortunate to have started a new security analyst gig  after finishing FIREWALL and VPN which has been a great experience.  I would encourage anyone doing this track to keep going because this material is super relevant, especially with the new security track, I just wish there was some written material on it already.