Anyone who even, loosely, followed the presidential primiaries, or has ever heard Donald Trump speak, knows, the republican establishment can't stand him. From the rumors of the RNC changing the rules and proposing a "White Knight" candiadate, to the Trump and Paul Ryan debacle, to George H. W. Bush coming out in support of Hillary, one thing is clear: The Republican Party is imploding because of the rise of Trump, and after this election we will, most likely, see a very different GOP.
With Trump exploiting the populist anti establishment rhetoric that made himself and Sanders so popular, it's possible to speculate that Trump will hold true to his message, and the party will begin to distance itself from its cozy relationship with Wall Street. But, much like Trump's entire campaign, it will only be a facade that will trick the general public into thinking he's acting on principle when in actuality he's making shady backroom deals left and right. For example, while claiming to be self-funded, 33.7% of donations came from outside sources and most of his own "self-funds", most were loans that he would launder back to himself.
What I think we are likely to see, is a new hybrid Republican Party that moves further left, while simultaneously moving farther to the right, even further than the Neo-Conservatives. On the one hand, we could see a Republican Party that advocates for universal maternal leave and childcare, denounces free trade agreements, imperialism, and cuts to Social Security, Medicare, and Medicaid, while, on the other hand, calling for the profiling, and banishment of all Muslims, the expulsion of all undocumented immigrants, regardless of circumstance, and the abolition of international law, with regards to torture and the Geneva Conventions.
Of course, none of these could occur, and Donald Trump gets impeached on day 4 for lending Vladimir Putin a copy of the President's Book of Secrets, resulting in no change to the GOP as we know it.