At the start of the 360, PS3, and Wii's lifespan, there were many who didn't believe in the feasibility or popularity of downloadable games. Now as we're nearing the end of the generation many have since changed their minds completely. Although no company ever said they had plans for maintaining your digital library down the road, it was not something many worried about.
Sony Worldwide Studios' Shuhei Yoshida made comments today to burst the hopeful bubble that some had been forming as the PS4 was announced. Here is what he said when asked about PSN games working on PS4:
"No. Unless, somehow, some games work on emulation. The easiest thing technically would be to make PS1 games work on PS4 through emulation. But we aren't talking about our emulation plans as yet. There are two ways: emulation or cloud service. But native support, no, sorry. We could do so if we choose to. We know who purchased what as a record. But we are working on service plans, and we haven't decided."
So the word at the moment is no. None of your PSN library is going to be transferable to the shiny new PS4 unless Sony makes the effort to get them running, thanks to different system architecture. Recall that Sony received negative reaction after previously suggesting that the Vita would have a way to transfer UMD games for PSN copies. While the service came to Japan, other territories never gained access to it. That is probably why Yoshida had to deliver his response with a fairly strong "no."
Did you expect that PSN games would transfer to PS4?