Trump saying he won't be going after dreamers (for the time being, anyway) reduces effectiveness of them being used as political leverage talking point.
At this stage in the game, during these tumultuous times, and to deport large numbers of the decidedly more criminal types in the most politically orderly fashion (which Trump does have plenty of support for) Trump has to go easy --- where he can go easier --or at least look like he's being reasonable.
In end game strategy --- I'd say; ok, "dreamers" of the class here in the U.S. prior to --what was it -- the year 2011? --- can stay -- but politically speaking, at a price.
Stop, put an end to Illegal Immigration. Then, increase LEGAL Immigration (but at a price -- NO MORE ANCHOR BABIES).
That's a political formula that would be difficult for the Left (I mean, the Democrat Party) to not agree to. If the Democrats dug in their heels -- it would wreck them for at least decade -- during which legislation could be shoved through having even less Democrat Party input than they have leverage for now, at the moment.
Support the Dreamers in something along these lines (but wait for the last 24 to 18 months of his term to bring it out more fully visible on the table) and a second Trump presidential term could be all but guaranteed.
Strategic thinking of the kind you outlined is beyond the ken of knee-jerk Trump-bashers, whose only consideration appears to be a need for instant gratification of their rigid dogma...