Hopefully, nothing valuable (such as a diamond ring) will be in that water, because after the water flows down the drain, it is gone forever.

希望没有什么贵重的东西掉在水里了(比如钻戒)，因为水流进下水道就收不回来了。

youdao

All had promised not to do drugs, smoke or consume alcohol for at least two months, hopefully forever.

FORBES: Creative Giving: Somebody cares

By comparison, both Google and Apple rest as undervalued properties, hopefully not forever.

FORBES: Google And Apple: Why I Own Them Both

Hopefully, I stay here forever.

WSJ: Gardenhire, Girardi, Manuel facing the pressure