Nor should they push the button. This needs to drag on through the election periods for other EU countries, in particular France. Whilst this is hanging in the air, it will fuel the appetite for referendums across the EU and see its eventual demise.Not yet it isn't! nothing has changed.
Every day that passes adds to the uncertainty as the other side is showing no sign of being willing to negotiate, and our Parliament is terrified to push the red button.
Given half a chance they will come up with reasons not to and it will gradually founder and be forgotten.
A really good sign would be if they find some new war to wage to divert public attention away from it, first adding a delay and finally in due course when enthusiasm dwindles it will evaporate.
The EU are desperate for us to pull the trigger on 50. Each day we don't strengthens our position.