Where did you read such bullshit? There is plan in some far future to standardize railway gauge in all EU to 1435 mm, but that includes not only replacing 1520 mm in Latvia and Lithuania, but also 1524 mm in Estonia and Finland, 1600 mm in Ireland (sounds stupid, why to replace anything on an island) and 1668 mm in Spain and Portugal.

Only active project regarding 1435 mm currently ongoing is Rail Baltica, but that's nowhere near completion (will connect Tallinn to Warsaw) and has big funding problems (due to costs rising multiple times, as it always happens with big government projects).

Btw, before World War II both 1520 mm and 1435 mm tracks were operational in Latvia in parallel, but 1435 mm got demolished by Soviet Union. Back then you could go with a single train from Riga to Paris ("Nord Express").

But, yes, Russia is very dependent on railroads for logistics. Even before full scale invasion into Ukraine began, lot of experts ananlyzed that biggest problem for Russia could be not enough trucks, not not enough tanks. Good that Latvia have already demolished some rail lines going to Russia that wasn't in active use anymore, only single line to Russia and single line to Belarus are left (used for cargo only).