From my understanding he's offering a pathway to citizenship to the 1.8 million potential DACA recipients currently in the u.s.
That will be after 10-12 years in the U.S.
What the criteria to gain citizenship will be will probably be stiff (must speak english, no criminal record, etc).
As well, by signing up for protections you pull yourself out the shadow for scrutiny.
Honestly, some probably won't meet the criteria to become citizens and be deported, some will self-deport, some won't even sign up for the DACA extension and remain hidden, some will go back to mexico, gain their citizenship there and try to apply another way to save time, some will become citizens.
All this along with the inability to bring your entire family the the U.S disincentives citizenship and will cause a lot to simply self-deport. That and if they put limits on remittances...
Smarter move than mass deportation honestly.
Not saying i want to see people deported or not to become citizens btw, just pointing out that it's a smarter way to handle than mass deportation.