Donald Trump's immigration stance is now close to the views of mainstream politicians. He has abandoned his position of creating a force to round up and deport all of those staying here illegally. He has now stated he would only deport those that commit crimes, mirroring a position held by Democrats Clinton and Obama.
Yes, Trump's stance on immigration is more closely related to the mainstream politician stance. Initially, he advocated for complete removal of all undocumented immigrants, regardless of the time they have spent in the country. However, at this point in the election, he has softened that stance and is advocating that many of them pay back taxes and stay in the country, just without citizenship. This policy is more akin to that of other Republican candidates.
The one constant thing about Donald Trump is that he just says whatever sounds like a good idea at the time. One day he wants to keep everybody out, but the next he realizes that's going to kill him in the election, so he reverses course. But that second course isn't any more genuine than the first, he just thinks it's a good idea to say now. Voters see through this kind of stuff, and even if Trump co-opts Hillary's immigration position we won't be able to trust it because he's such a loose cannon.
Trump changes his positions so often, he can't be described as mainstream because you don't know what he's really thinking. After all the talk of building a wall, now he wants to basically adopt the Jeb Bush plan that he mocked just months ago. He is desperate at this point and changing stances to try to win votes.