I don't see that it would be a problem for Eladrin to lose the bonus if they go Int/Cha (but only if).
Which is my prediction for what the Eladrin alternative to Dex will be (stolen from someone, but obvious). Str and Con make no sense; 4e Eladrin == 3e "Grey Elves", who got a penalty to Str and Con; Wis would make them identical to elves with a different primary (and doesn't make much sense), and Cha is the primary Fey stat. This does risk making them identical to drow (but with a different primary stat) if Drow, as seems most likely, get to swap Dex for Int, but that's probably acceptable. If not Cha, I'm guessing that it will be Str, yes; this will make Eladrin excellent fighters and let them compete with Dwarves for the "best defender" race.