JS, Israelites aren't the only stubborn unbelieving peoples that God might think worth going to such lengths for. But with that said, I don't think speaking in another (understandable) language would seem as miraculous these days, given the accessibility of language learning tools that are so readily available today.
1Cor.14:20-22
20 Brothers and sisters, do not be children in your thinking. Instead, be infants in evil, but in your thinking be mature. 21 It is written in the law: “By people with strange tongues and by the lips of strangers I will speak to this people, yet not even in this way will they listen to me,” says the Lord. 22 So then, tongues are a sign not for believers but for unbelievers.
No such "promise" given to Gentiles. Is.28:11
Of course there is also the problem that Paul said not all will be given the gift of tongues 1Cor.12:30 so no-one can insist all must speak in tongues.