No, it's actually been happening for a few years now.
Before Trump even was a blimp on the radar.
Pew Research Center-
Mexicans made up 52% of all unauthorized immigrants in 2014, though their numbers had been declining in recent years. There were 5.8 million Mexican unauthorized immigrants living in the U.S. that year, down from 6.4 million in 2009, according to the latest Pew Research Center estimates. Meanwhile, the number of unauthorized immigrants from nations other than Mexico grew by 325,000 since 2009, to an estimated 5.3 million in 2014. Populations went up most for unauthorized immigrants from Asia and Central America, but the number also ticked up for those from sub-Saharan Africa. Increases in the number of unauthorized immigrants from other countries mostly offset the decline in the number from Mexico.