It will switch to the new environment when she finishes the 3rd grade curriculum (or starts hitting some 4th grade units, not quite sure).
The units themselves will still be presented in a similar format, but the story threads in the adventure park go away and you switch to a simpler lesson picker -- a bunch of lessons you are working on will show up, with names (open number line, fractions...), and you pick from that, and you get checkmarks when they are completed. Every once in a while you unlock a movie with some upper elementary humor that is actually a mini-lesson -- I really liked the one that compared algorithms for doing additions, trying to show different techniques work best with different numbers.
The little game park goes away, and there is a space where you can unlock less obviously mathy games. I found that part pretty meh.
DS7 was very happy when he switched to the new environment last year toward the end of 1st grade, but he had been watching his brother play for a while and is very competitive, so part of the attraction was feeling grown up.
We have been using Dreambox for a few years, starting before the new environment. With my eldest we did hit a point in the 2nd or 3rd grade curriculum when we had to stop/slow down for a while and drill on math facts, because all the mental math units were becoming very frustrating without automaticity.
