
This post looks at statements made in the 2018.1 and 2018.2 versions of the PetaLinux Tools Reference Guide that seem to indicate that Xilinx decided against removing HDF files.
Warnings Removed?
The 2018.2 version of the PetaLinux Tools Reference Guide contains this:

What does DSA stand for?
From page 20:
Note: Device Support Archive (DSA) is hardware description format introduced in Vivado. DSA is super set of HDF holding additional configurations that can be changed by XSCT/XSDK.
"Removed DSA warning and recommendations throughout the book"
I compared the 2018.1 and 2018.2 versions of the PetaLinux Tools Reference Guide. Here were the differences of substance:
Note: In the following differences, 2018.1 is on the left and 2018.2 is on the right.
#1 (page 20,21):

Highlighted: In 2018.1 it says: the HDF file will be deprecated in the future releases of Vivado and PetaLinux. Currently, PetaLinux supports both HDF and DSA files. In 2018.2, this warning is not present.
#2 (page 24):

#3 (page 127):

Highlighted: 2018.1 is missing the line: AMBA, AMBA Designer, Arm, ARM1176JZ-S, CoreSight, Cortex, PrimeCell, Mali, and MPCore are trademarks of Arm Limited in the EU and other countries
Commentary
A Google search for site:xilinx.com HDF deprecated turned up no other relevant info, like an announcement from Xilinx.
Call to Action
Do you know what the story is with the DSA vs. HDF? If so, post a comment.
References
The 2018.1 [link] and 2018.2 [link] versions of ug1144-petalinux-tools-refence-guide.pdf were compared using https://draftable.com.
Xilinx logo found via https://twitter.com/xilinxinc at [link]
Other Info
What is a CR update?
CR update is not defined in the document.