Amidst the news that Bloodborne will be a part of March's PS Plus lineup, Sony announced that there will be some changes coming to the service starting March 8, 2019. On that date next year, the PS Plus monthly games lineup will focus on PS4 games, and no longer offer PlayStation 3 and PlayStation Vita games as part of the service.
Sony says that this will not affect any of the game already downloaded, or offered for download prior to next year's March 8 date. Those games will remain in players libraries for as long as they are subscribed to PS Plus. The only change is that PS3 and PS Vita games will not be offered past next March.
Sony also confirmed to Polygon that the PS Plus lineup after February 2019 will only consist of two PS4 titles, meaning that rather than filling the gaps left by the PS3 and PS Vita games, Sony will be whittling down the amount of free games offered to players down to two.
This move isn't wholly surprising. It's been five years since the PS4 debuted, and nearly 12 since the PS3 first launched. As the console generation phases forward, and with companies possibly looking towards PlayStation 5, there is no reason to support a console not long for this generation.
It remains to be seen whether or not this new focus towards PlayStation 4 titles mean that there will be stronger games added to lineup each month after February 2019. Microsoft for example has thrown in first-party titles into its Xbox Game Pass service (separate from Xbox Live Gold which comes with its own PS Plus-style monthly free games).
Either way, starting next March we can expect no more PS3 and PS Vita games coming to PS Plus members each month. We will mourn their losses, especially for the Vita.