Aren't you guys assuming PS+ will be the same as this gen which makes no sense. An extremely large amount of PS4 owners will be getting it anyway for online, what reason would Sony have to essentially give away games to people that would own the service anyway?
1. What they've announced so far is better than what the Vita had at launch. Once the Vita had a library to pull from the PS+ offerings exploded.
2. Why do you assume PS+ is strictly used as a way to get $50 a year from gamers, or that once they have that revenue coming in already they'll feel no incentive to continue?
Look at the games offered on PS+. Do you think Sony is making oodles of cash off of it giving those games away as it stands now? I don't.
Instead, it looks like a reasonable system whereby the can subsidize publisher costs to create a game "club" a la cheese/jam/wine of the month clubs. Much like those set ups Sony uses bulk purchasing to get incredibly friendly deals, then distributes those to gamers. In short, if publishers are finding value in selling a specific AAA title over Steam for $5 years after it's release and netting an extra 100k sales why do you think they'll suddenly disagree with getting $3.00 each from 10 million PS+ subscribers instead? When they have a sequel coming out in two months? It adds up. The more PS+ subs the more buying power Sony will have.
But lets take that one step further - what kind of games have we seen? A lot of games with sequels or new DLC just releasing. A lot of smaller titles that wouldn't get much publicity otherwise, but that are high quality titles. A lot of older games past their prime that were well received critically but missed at retail. In short, it's free marketing.
Why do you think they're going to suddenly curtail the library of games when the distribution of said games is 1. cheap and 2. free marketing for the parties involved?
If anything I'd expect the offerings to grow and improve as they bring more people into the club thanks to the online paywall. 3rd parties will be much more interested in using it for promotion of franchises and to squeeze out every last penny of profit on older titles a la Steam sales.