The question is, how will they balance a hardcore gaming community which hates paying to get better (stats-wise) items vs monetizing F2P? Will they charge only for cosmetic items, or will they drive away their core Dota fanbase?
Let's consider:
* Replay system
* Training system
* Coaching System
* Microtransactions
* Trading interface
* Community Submissions + submission royalties
Who knows what else? At this point, I think tf2's success is going to influence DOTA2, and I wouldn't be surprised at all if DOTA2 is released free to play.
I probably won't ever play DOTA2, but I'm thankful for all the improvements to tf2 over the last few years. I'm just hoping for some mainly bug fix patches to be released soon as this point.
The Degreaser flamethrower in TF2, for example, is a non-stock item that lets you switch weapons faster, but also reduces the burn duration of enemies you set on fire.
Hell, you don't even need to be trying to monetize to screw this up. See: Modern Warfare multiplayer and its propensity for handing strictly better weapons to veteran players, resulting in even more lopsidedness in matches.