No, there is no major layoff that is going to happen. It is all going to happen under/without WARN because Qualcomm themselves HAVE NOT posted a strategic realignment plan like they did in 2015. Mid January they said they will have a 1BIL cost reduction program, and San Diego Tribune sources say it's mostly going to revolve around winding down pre-consumer R&D on 5G, administration overhead, and QTL.
SRP - RIF for 2015. Nothing like this has been posted for 2018 announcement for 1BIL 'cost-reduction.' In 2015 it was specifically called a RIF and SRP.
https://www.qualcomm.com/news/releases/2015/07/22/qualcomm-announces-strategic-realignment-plan
You will NOT hear anything official on April 18th.
Hope this helps :)