Well, so far there’s rumors that Dallas will offer KP the max right out of the gate, they’re going after Kemba (another max), and then after Horford at at least $25M+.
They can probably get two of those but not all three unless they move significant salary, which looks unlikely. If they’re offering KP the max out of the gate, that’ll leave them with either Horford or Kemba.
Have to think Kemba finds Boston more attractive than Dallas, as by adding him we’re a big guy/major Timelord jump away from contention right now. Even signing Kemba and KP this summer, I don’t see them competing for a championship in the next few years of Kemba’s prime, especially with the uncertainty of KP’s injury.