Ah, but this is semi good news: Baltic states examining whether a Tallinn-Riga-Vilnius train on existing broad gauge infra could be possible https://www.railwaygazette.com/baltic-states-discuss-vilnius-riga-tallinn-passenger-service-and-gauge-conversion/63439.article

It's not at all hard to do. And that - together with coordinating timetables at Valga, extending Vilnius-Turmantas servics to Daugavpils, and running something on Jelgava-Šiauliai - are not at all complex

There's no time frame of course though...