There is a *HUGE* warbird presence at AirVenture. Enough of them to see to keep you busy for a very long time. True, if you simply count raw numbers of aircraft showing up, the "North 40" and other camping areas are full of spamcans.... the numbers are in the thousands whereas the number of warbirds may only be in the hundreds... still that can keep you busy for a large portion of your time visiting there.
Oshkosh/AirVenture is a gigantic event. Even if you stay all week long and camp out on the field, it's impossible to see everything. You'll still have to pick & choose what you spend your time on.
I've been going for 5 years in a row now, and this will be my 6th.
Here's a must-see video from AirVenture 2009 that'll give you a little taste of what its like to be there: http://www.youtube.com/watch?v=nKU0uQki5Dc