I wonder how many more minutes until the train comes.
How much longer do you think until the train gets here?
後どのくらいか時間を聞きたい場合、次のような聞き方ができますよ。
ーI wonder how many more minutes until the train comes.
「後何分で電車が来るかな」
I wonder how many more minutes until ... を使った聞き方。
ーHow much longer do you think until the train gets here?
「電車が車で後どのくらいだと思う?」How much longer do you think until ...? を使った聞き方。
ご参考まで!