I'm skeptical. While it would be great to try before I buy, companies aren't thinking about that these days. Companies, not realizing that demand drives prices, can't understand why people don't pay more for the same product they are already getting. I mean, movie companies seem to think $1 per viewing is too little for a movie (this Redbox is evil). $1 per song is too little (thus iTunes is evil). And $15/month for as many moves you can move through the mail 3 at a time is too little (thus Netflix is evil). Not only that, but not getting more money when a product that's already been paid for is resold is really bad (thus Gamestop, Thrift-stores, used book stores, etc.. are true evil)
No, expiration won't be for the purpose of giving more to the consumer. Rather, they'll probably use it to turn off games they don't want you playing anymore (why play Madden 2009? Madden 2010 is already out!!!).