Will systemd become standard on mainframes as well?
doubtful. I think the 'culture' that produced things *LIKE* systemd aren't in line with IBM's way of doing things...
IBM really is about giving customers what they want. If customers DO NOT WANT systemd, they won't have to use it when IBM gets its way.
Think "sales and marketing" meets "engineering". The reality is that engineering needs sales/marketing, even if they're irritating as hell and drive the process too often, because it's the CUSTOMERS, and not the whims/wishes/unicorns-and-rainbows of the engineering team that get the development time assigned. no more "because we *FEEL* and people MUST accept it" (the attitude behind things *LIKE* systemd and gnome 3) is what I expect in the future... from IBM's hand in the mix.
After all - IBM has invested their future in Linux. No doubt they want THAT to continue.