The slow rate of change of things like Congressional District boundaries, combined with the ability of legislatures to gerrymander, means that at the local and state level the effects of the Great Replacement can be held off for a bit.
But at the national level I don't even see 10 years. If Trump loses (or maybe even if he wins) it's the end for the GOP and Conservatives being in the White House.
The Dems may eventually be putting both candidates up: one from the Hillary wing, one from the Bernie wing. The GOP will re-brand itself in a way that will shock and appall most current supporters. We will look back fondly on psedo-conservatives like Romney when we see what the GOP is running to win in 2024 and 2028.
I don't know what you define as a bit, but in the grand scheme of things, it will be like trying to hold back the tide. Red and Purple states trending blue will predominate. And once TX goes, it is all over.
When the history of the rise and fall of America is written, historians will point to the 1965 Immigration Act as the most consequential act leading to our demise. We are now seeing its dramatic impact. When you import 35 million legal permanent immigrants since 1990, 87% of whom are minorities as defined by the USG, there will be electoral consequences. Immigrants and minorities vote more than two to one Dem. We are being colonized by the Third World.