The Bolsheviks do better in 1919 (perhaps 1920, but I have a gut feeling that this would be less probable) and overrun all of Lithuania. Poland then kicks them out when its armies advance eastwards and ends up controlling the entire country. What happens next depends upon who is running Poland. If Piłsudski has his way Lithuania becomes a theoretically equal partner in a federation with Poland. If the National Democrats prevail they will try to simply annex it. If the Entente doesn't like it they can probably get away with granting it some kind of autonomy which may or may not be meaningful.