To first directly answer your question, no, I personally don't believe that the members of "Mlada Bosna" ("Young Bosnia"), the Serbian Nationalists that assassinated Franz Ferdinand knew of his personal political views.

Most of the assassins and members of "Mlada Bosna" in general were college students under the then legal age of 21, so in the eyes of the law the were little more than children that just happened to have a political goal that they were very passionate about. To 'em and many at the time there was just something noble and poetic about the idea of Slav freedom and unity, that's why many didn't care if the got caught afterwards as long as the long term goal was met. That's just something that was always true and still is, that when people get passionate 'bout something they tend to not listen or think rationally.

From a logistics perspective there is little chance that they knew of Franz Ferdinand's personal political views, the same way you likely don't know the long term goals of your government or ruling elite.

Like they say in The Great War podcast Franz Ferdinand was the minority with the idea of further splitting up the country and further weakening Austria's power within it. Even the Hungarians got their autonomy as a compromise after the bloody Hungarian Revolution of 1848, so i doubt that they would have just given it freely to the Slavs too.

You could also doubt the effectiveness and unity of a country split in three different entities and run by three completely different ethnic groups, such a country facing any major obstacle would most likely collapse, which's exactly what happened near the end of the first world war.

But even if the country were further split in to a third entity, the Slavs in Austria-Hungary were not a homogenous people group, there were of many different religions, languages, cultures, historical backgrounds and each with their own view of the other and both the Austrians and the Hungarians. You had the Czechs, Slovakians and Poles all Western Slavs, predominantly Catholic, you also had the Ruthenians who are Eastern Slavs, mostly Eastern Orthodox and finally you had the South Slavs (Slovenians, Croats and Serbs) who came in many different religions ranging from Catholic and Orthodox Christianity to Sunni Islam, although the Muslims nowadays identify as Bosnians they're mostly other South Slavs that have adopter Islam with the arrival of the Ottomans. So even adopting a tripartite state would most likely resolve little, causing the smaller Slavic communities to be dominated by other bigger Slavic groups.

On a final note "Crna Ruka" ("The Black Hand") the radical group based in Serbia that provided weapons for the assassination of Franz Ferdinand were also known by their slogan "Unity or Death", so in that regard they were pretty determined and I doubt that a tripartite state would have appeased 'em.

This's mostly just a guessing game, so a certain amount of assumptions have to be maid , 'cause it's borderline impossible to know what people throughout history have exactly known and what they haven't.

If you disagree or if I've missed something, feel free to correct me.