Let's be real: Alonso can't really think he has a competitive drive next year with McLaren.
I'm not saying that Button meant, that Jonathan meant, that Alonso is (also) in talks with McLaren to STAY next year. But he surely doesnt want to play catch up with Manor and Haas next year.
What I think (and hope for Alonso), that he has some kind of exit-clause when the Car is not competitive. So McLaren tries to talk Alonso (and apparently Button) out of activating his exit-clause.
If Alonso would be confident that the care is competitive next year, he would try to get more data for his Team, knowing that this season is datamining for next season. But he isnt playing that part ("Alonso we need fuel-data" "NO! I want to drive!")
So either he wants out this year or he is just doing a Kimi and collects his paycheck. OR he is just a diva, a non-teamplayer, that just wants everything on the silver platter and expects the team to magically get the car good next year.