While it can be hard for those flying within France to hit Elite Plus with the upcoming change, you have few ways out to keep your E+ card.
If you are Ivory it's gonna cost you a lot to hit Platinum with Air France since your XP points will restart when you reach your next level. Starting from Ivory, you will need a whopping 580 XP for Platinum. For more info, you can check the good sum up of zetravelersclub : http://thetravelersclub.boardingarea.com/nouveau-programme-flying-blue-comprendre-qualification-hasardeuse-statuts/
BA was the same when I signed up back in 2009. But it was much easier to qualify.
I'm just sharing how many one-way trips you need to make to hit Elite Plus with Skyteam partners (I put the least demanding ones):
MEA - Cedar Miles :
Must be done on a calendar year (01 January - 31 December)
Air Europa - SUMA :
Once you hit Gold or Platinum you have 12 months to achieve the above requirements to keep your card.
Saudia - Alfursan :
I will soon outline the same for Star Alliance and OneWorld.
Will you stick with Flying blue or you are jumping ship ?