A lot of interesting speculation on this thread.
I saw from first hand experience that when HP "merged" with US, we got the worse aspect of the two programs bennie by bennie.
HP had free drinks in their clubs, US didn't, free drinks went away.
US allowed top tiers to carry over all EQM's over 100K to the next year, HP didn't, went away.
US gave top tier valuable transatlantic upgrades, HP didn't, upgrades became impossible to use.
HP cleaned their aircraft, US didn't, they are all dirty now.
HP top tier at 75K, US 100K, now it takes 100K.
I could go on (and on), but you get the drift.
I left US after 22 years of loyalty and fly UA for E+ and SWU's and excellent saver award availability. If these go away, I will be looking for another carrier. At least it won't feel like a divorce this time as the marriage has been so short.