They would have stepped down from their DQ assimilation but continued to boost their ranks by assimilating the AQ and the BQ. The Feds would not notice that they went quiet in the DQ, and they would be kept busy by extra AQ Borg fronts. Meanwhile back in the DQ all efforts would be expended on assimilating or integrating Species 8472 properties into the collective in order to be resistant to such a puny virus as Icheb's puny world came up with. In order to keep this project from hostile forces (ie, everyone else) all contact with the AQ and BQ would be severed, lest a freed individual should report this alarming information to their world and all eyes should turn to the DQ, hindering their progress.
Eventually they would succeed.
Within a span of a decade all the Borg of the DQ would be more Species 8472 than not. When they returned to the AQ and BQ and they would view the Borg there as inferior prototypes. Their assimilation of the non-8472 Borg would be seen as hostile and a Borg on Borg war would break out.. which would be quickly over when the DQ Borg assimilated or destroyed all inferior Borg.