お先さき真まっ暗くら

na-adjective, noun which may take the genitive case particle 'no'

very bleak outlook; dim prospects

Describes a situation where the future looks hopeless or extremely unpromising. Often used in a resigned or pessimistic tone.

• このまま成せい績せきが下さがり続つづけたら、進しん学がくはお先さき真まっ暗くらだ。

  If my grades keep dropping like this, my prospects for further education are very bleak.

• 会かい社しゃの業ぎょう績せきが悪あっ化かして、将しょう来らいはお先さき真まっ暗くらな気き分ぶんだ。

  With the company's performance worsening, I feel like the future is completely dark.