Yeah I'm pretty confident S5 touchwiz magazine style cards will basically just act like my magazine on note 3 and sit on top of touchwiz as it currently is.
I doubt other than the cosmetic change of it, there will be NO changes to touchwiz underneath and that us why the s5 will come with 3gb ram. Simply because it will HAVE to.
I doubt we will see any rejigging of the criminally out of date Dialer, contacts, messaging, clock, gallery etc.. And likewise Little if Any optimisation or reduction of the myriad of bloat apps and features.
We will simply see a new app that looks nice but just sits on top of everything else and hey presto - that's touchwiz 2014 sorted.