Yes, this may happen. As you say, the test is adaptive. A few notes:
-The mba.com exams, while in most respects the best simulacram available, doesn't seem to have the same depth of very hard quant questions as does the real GMAT.
-The questions don't really come in buckets of 600-700, 700-800, etc. Each question has its own degree of difficulty (go google "item characteristic curve" to learn more, or read Stacey's excellent primer here,
http://www.manhattangmat.com/gmat-uncovered.cfm).
-Just two days ago I got a note from a student who reported that the real GMAT seemed easier than either the mba.com exam or our CATs. He earned a very high score (750) and his Q was just one or two points lower than your practice Q. So...your mileage may vary. I suspect that he either didn't realize how hard some questions were, or peaked right at the end of the Q.