They would absolutely keep it a secret for as long as humanly possible.
If they had a body double stand-in for her as a means of preventing Trump from nominating a replacement, the lefty media would in lockstep play along, without exception, and would insist that it was the real one and anyone saying otherwise was a crazy conspiracy theorist.
And they would repeat it over and over and over enough times until they themselves actually believed it.
>If they had a body double stand-in for her...
Headline: RBG converts to Islam! Will always wear burka in public.