[O__________O]

Only if you consider a 100 year old border a dire situation. Otherwise it would make way more sense economically for Russia to offer to resettle anyone interested no longer being Estonian instead of invading yet another sovereign country.

[throw-ru-938]

The present border is more like 80 year old, it was adjusted by the USSR (favouring Russia) after the Baltics were annexed in 1940.

However, it generally follows the pre-1917 borders of the Governorates of Estland and Livonia.

[O__________O]

Map showing the annex your referencing:

https://commons.wikimedia.org/w/index.php?curid=352476

I was unable to find a map overlaying pre-1917 borders and current borders.