So I'm a bit confused - the demo armies were around 100~ points without upgrades and standard/full army size is 200 points including upgrade cards - so we're not looking at much bigger armies than those in the Core Set for standard sized games.
That seems odd to me - it's a rank and file system, which suggests huge armies, but we will in fact have 8-12 units - which makes it feel a bit more like a skirmish.
Why not go the whole hog and up the scale a bit?
While I can't speak for FFG, I think keeping the standard size at 200 points is a good idea. While moving huge blocks of infantry and cavalry up and down the table is a lot of fun, the higher your standard game size is, the higher is your barrier of entry. With all the tabletop games out today, many people will be reluctant to invest huge amounts of money and time (while I was away from the hobby, I always thought about getting back into WHFB, but the need to invest 800$+ and roughly a hundred hours of playing time always kept me back).
The way it looks right now, we are probably looking at a 200$ investment to get right into organized play. This is small enough for many people (like me) to give the game a chance on release day, even if they don't know how well it will be received.