There is a large number of packages currently build-depending on openssl 1.0 explicitly. Supporting dual-stack 1.0 & 1.1 openssl is a lot of work. In Ubuntu, I have reverted the 1.1 migration, and forced 1.0 to be used and provided by both libssl-dev & libssl1.0-dev packages. This was done after a consensus consultation with some of the ubuntu developers, archive admins, and security team. If the transition in Debian goes really well, I see Ubuntu picking it up for 17.10. Realistically, I see it for the 18.04 LTS cycle.
-- Regards, Dimitri.
