Y'all are thirsty for collabs with other females but I honestly think a) Katy sounds better solo b) she won't have collabs with other girls on her next album.
But in reality I think basing next era's prediction on the previous era is kind of a weird thing to do, because since when have two back to back eras ever been the same in terms of success? There's always some level of difference.
I think she can get at least 3 #1s next era. Don't bookmark, but I have a good feeling. It'll be somewhere in between PRISM and TD for singles success and album sales, her biggest tour and a new overall peak.