Anyone should be able to make between $4 & $5 per 1000 visitors from just running AdSense.
Use that as a baseline and do the math from there. If you can add-on non-advertising forms of revenue then that is a bonus.
It's going to depend on your field of course, but it's pretty easy to get between 0.5 & 1% clickthough and 10c per clicks. That's between 50c & $1 per 1000 pageviews, and I said $5 per 1000 visitors (ie, uniques). If you double the CTR (quite doable with optimization) and get 2 pageviews per visitor then that's $4/visitor already...
If you prefer, look at it like this. The lowest Adsense eCPM I've seen over any medium period by anyone I know is $0.70.
Posterous is doing around 1.5 million pageviews per day (http://www.quantcast.com/search.jsp?domain=posterous.com) and Tumblr is doing over 60 million.
Getting revenue with that much traffic wouldn't be too hard.
Thats similar to the way Wordpress played out.