The ps3 will probably have continued online support until a little after the ps5 comes out. So around 2020.
This is just an assumption. Honestly if you want it for things like netflix I highly recommend just getting a ps4. They can be bought for less then $200 used now. Are great for streaming and the games are next gen.
The only reason I would suggest the PS3 to someone is if they are collectors or if they don't mind playing older games and want to buy them cheaply. But at this point I don't think it's a good idea to have it as a streaming device.