Dànyuàn rúcǐ!
但愿如此!
I hope so!
Notes:
但(dàn): only
愿(yuàn): to hope
如此(rúcǐ): like this
Example:
A: 听说明天是个好天气。
tīnɡshuō mínɡtiān shì ɡe hǎo tiānqì.
It's said the weather will be good tomorrow.
B: 但愿如此。
Dànyuàn rúcǐ!
I hope so.