Via Instagram posted a picture saying "Big Brother Has Been Renewed for 2 More Summers! 2017 & 2018" as well as commenting "It's not #Summer without @ Cbs_bigbrother !!! #Renewed"
With that said BB19 is still going on for the Fall then they'll be BB20 (which is most likely a full returnees season, Allstars or Second chances not sure yet) and BB21.
I hope there are more seasons because I will be eligible to audition for BB22 :)