Honestly, whatever Estonia or Lithuania do would hardly directly affect total greenhouse gas emissions of our civilization. Given local geopolitics their first priority is survival and prosperity as independent states. If they can do it while getting and staying "clean" - and i think they can do it by using more solar&wind (and that will even enhance their independence) - great, and if they have to burn some natural gas - nobody will really notice given their size especially considering that natural gas is the cleanest energy source among the "dirty". While getting nuclear in any way for them would mean losing a bit of independence (that closing of their own NPP at the will of EU is a clear example that your nuclear industry decisions aren't really yours and are actually subject to the will of the bigger powers).