I actually wrote my IB History Internal Assessment on this, and I was curious as to what you guys thought might happen in such a situation.
Say something (We'll leave that "something" up in the air) encourages Jogaila to convert to Orthodoxy and marry a Russian princess, rather than the queen-regnant Jadwiga? Let's say some girl from Ryazan, being on the border with Lithuania, and being a relatively powerful Principality.
How does this affect Eastern European politics? Do we see some sort of Lithuanian-dominated Rus state emerge? How do the Mongol remnants fair against a Lithuania with much more interest in their Eastern border? How does this affect the religious balance in Europe? Will the Teutons have much more casus to their belli for their Crusades with Lithuania being Orthodox? Might one even see the Teutons being supported by Poland as allies against Lithuania? How does politics in the Baltic change?