There is a change coming to PlayStation Plus next year. For the longest time now if you are a member. There is a new list of games each month you can download to each of the PlayStation platforms, PS4, PS3 and Vita. The other day received an email and they all so made a statement in the blog post announcing the list for March 2018. Which you can read > here.
Starting next year (March 2019) they will focusing on the PS4. So there will be no games for PS3 and Vita to download. That being said any games you all ready downloaded or add to your library can still be played. Provided you are still a member.