How will climate change affect planetary waves?
As a non-climate specialist, this topic is on the edge of my understanding of meteorology, but here are some papers that I found potentially relevant to your topic. 

Here is a quote from the summary of Limpasuvan and Hartmann, 1999:


  The planetary wave propagation characteristics can be used to link
  changes in the tropospheric annular mode to changes in the strength of
  the stratospheric polar vortex during winter. Planetary waves are
  strongly attracted to polar regions during the low phase of the
  annular mode when the tropospheric westerlies are displaced
  equatorward. We should expect a weaker stratospheric polar vortex
  then, since planetary waves weaken the polar vortex by generating
  irreversible mixing.


And here is a quote from Shepherd and McLandress, 2011


  In particular, the tropospheric warming that is robustly expected from
  climate change leads to a strengthening of the upper flanks of the
  subtropical jets, which causes the critical layers on the equatorward
  side of the jets to move upward, and with them the Rossby wave drag,
  allowing more Rossby wave activity to penetrate into the subtropical
  lower stratosphere (Figs. 4, 5). Because the subtropics represent the
  critical region for wave driving of the Brewer–Dobson circulation, the
  circulation is thereby strengthened.


So my conclusion from these two papers (there is obviously a lot more detail in the full text) is that polar vortex will weaken, subtropical jets and Brewer-Dobson circulation will strengthen, and Rossby waves will penetrate farther south. Of note, neither paper seemed (to me) to indicate that a cooler stratosphere was predicted.