◆pie in the sky
LONGMAN's definition⇒a good plan, promises, or idea that you do not think will happen (ex.)Building a baseball field downrown is just pie in the sky right now.--see also easy as pie
COBUILD's definition
If you describe an idea, plan, or promise of something good as pie in the sky, you mean that you think that it is very unlikely to happen. (ex.)The true regeneration of devastated Docklands seemed like pie in the sky... /He can't help thinking it's all just 'pie in the sky' talk.
↓ The social security system reform plans turn out tobe mere pie in the sky.
↑ （衆院解散・総選挙をにらみ、国民に負担増を強いる財源論議が下火になれば）社会保障制度改革は絵に描いたもちになる恐れがある。
◆pie in the sky ： 絵に描いたもち、当てにならないうまい話