Actually, I don't think Earth Prime/New 52 earth is changing that drastically post CONVERGENCE. I think the new suit/power thing is just for this storyline and will likely not affect the DCnU Superman in his other books.
Although....I do wonder if the New Earth 2 may be a refuge for the survivors of CONVERGENCE to live on. A place where Pre-Crisis JSA, Post-Crisis Superman and the others co-exist on together....a hodge podge earth if you will....or, as you said, something like Pre-Flashpoint DCU, which actually was starting to resemble Pre-Crisis Earth II anyway (married Superman....Dick Grayson had taken up Bruce's mantle alongside his offspring...etc).It actually would be a return to the Pre-Crisis status quo of EARTH 2 being home to the legacy heroes and the JSA...EARTH 1 (or DCnU) as focusing on the main JLA without a JSA or few legacy characters.