If you already have K-70 and don't feel limited by it --> No.
If you are beginner looking for first DLSR --> No.
If you already have a Pentax system and need to upgrade for the next couple years --> Yes.
If you need one of the features the KP has, or really enjoy its aesthetic --> Yes. (Aesthetic, size, grip ergonomics can be really important when choosing camera, I always recommend you go to a store and hold both in your hands to see which you fall in love with)
But honestly, since the K-S1 all the Pentax DSLRs are really great. They look good, they have lots of features, great viewfinder, buttons and ergonomics,..
Pentax K-S2 vs. Pentax K-70 vs. Pentax KP - Pentax Camera Comparison - PentaxForums.com