Morwen, I didn't say that JRRT meant his mythology to replace others. Personally, I consider all mythologies to be equally fictitious, but JRRT had at least one that he considered "truthful".
Back to the subject; besides my feeling that having Elves appear in the modern world would require events no less than catastrophic, all of them should have 'faded' by now, as JRRT put it, becoming veritable shades. Having any number of unseen voices begin spouting 'Elvish wisdom' or new and portentious dooms would either raise a big stir or get people locked up. Even if the End
wasn't near, the effects of an Elvish 'invasion' after so many years wouldn't be pleasant.