It'll never happen. Well, not in the next 10 years at least.
Case and point:
The largest part of all software that's used on this planet would not be usable.
Does anyone remember the "competing" digital video format when DVDs just hit the market? I may be mistaken, but I think it was called Divx (as odd as that is). The way it would have worked is you would buy a Divx player that would have a modem built in. If you wanted to buy a movie they would only cost about $5, initially at least. You would get about 3 plays for free, but every viewing after that would cost a couple dollars. The technology didn't lack in "backers" either, I don't remember many of them, but Disney was on the list. Well, long story short, it flopped. So much so, that most people probably don't even know it existed.
People are stupid, but they weren't stupid enough to buy in to paying Disney $2 every time their 6 year old watches <insert Disney title>! And we're certainly not stupid enough to buy in to this.