First, I'll say if you think SRE is new you haven't read the book or been around this part of the industry that long.
He addresses DevOps in the book. SRE and its concepts have been around longer. "DevOps" has a larger scope, but effectively the same approach to the problem SRE tries to solve.
Both terms are widely abused in the industry, in the public, and quite obviously on Slashdot. I can understand the confusion. So let's look at the job titles and terms' usage in industry:
As far as job titles go, my own experience in the Bay Area/Silicon Valley is that "SREs" can be divided into two camps: legit SREs at Google and rebadged System Administrators in lesser engineering organizations. Getting an SRE position at Google isn't easy, candidates really need a thorough understanding at every level. SREs elsewhere tend to be limited to basic Bash scripting.
Most DevOps (but not all) tend to be software engineers or release engineers first, with varying levels of ops or sysadmin experience.
Most in the DevOps movement never thought there should be a DevOps job title, and would mostly agree with the SRE principles practiced by Google... so I don't think they'd be too upset about "DevOps being replaced by SRE"