Republicans are definitely setting themselves up to be the undisputed minority party on a national scale for an extended period of time in the not too distant future
Yeah, this, rather than never again electing another president, is the plausible worst-case scenario for the GOP.
But the scary thing for the GOP is that it's a very plausible worst-case scenario given demographics, recent election history, but also political history. The presidency, the House, and the Senate have all been competitive since at least 1994, but it's pretty common historically for one or more of these institutions to be dominated by one party except in the case of wave elections. For example, from 1932 to 1968, Democrats controlled the presidency for 28 of 36 years, and controlled both houses of Congress for 32 of 36 years.
I could also see a scenario similar to the period from 1874 to 1894 where the GOP dominated the Senate and the presidency but Democrats dominated the House. Except in this case, Democrats would dominate the House and the presidency and Republicans would dominate the Senate.
