If it follows the formula most people scream about on this forum (we want more pops, more provinces, more army types, more resources...), it won't be successful, I'm afraid... Maybe Paradox should really consider changing its current philosophy towards not only automatization, but a certain reliance on game mechanics that can only be influenced, not controlled.
From my point of view, Victoria can be a great seller only if it manages to become the game that "allows you to build a national state". Meaning its political, ideological and cultural features should be more important than in Victoria 1.
a) Introduce head of government/head of state names... at least for the most important nations.
b) Emphasize the national aspect of the period.
c) Transform the peace years into a period dominated by reforms (more and less important than the ones in Vicky 1), inner politics and "Great Power" diplomacy and not by trading or promoting pops.
d) Don't just make more provinces; at a certain level, quantity becomes a burden.
e) Historical atmosphere. Playing France should not resemble playing the US.
f) Making pops into factors, not actors. Many people are satisfied only to see a list of people living in their state, ordered by ethnicity/religion/militancy/ideology, capable of being influenced by reforms, events, immigration, famine etc...