At the time overwatch is going to be f2p (and i hope and expect it wont be) things will go south. I am more interested in the idea of buying a game and get all the extra goods by actually playing it, than go for a small price (or free even) and buying all the stuff afterwards. It also drives away kids that are not so sure about playing the game. Plus blizzard is going to put effort in keeping the game upgraded via minor and major patches without adding any extra cost, except expansion packs.
That's my 2 cents.
Edit: I saw people talking about microtransactions in overwatch. Yes the game has a currency which you get from loot boxes to buy stuff. That's it.