However, what if the action is to take place in the future? We would use “will” for the future tense, and the past subjunctive of “will” is “would”, so, in accordance with the general rule, we say:
He will not do his homework. → I wish he would do his homework.
It will not rain tomorrow. → I wish it would rain tomorrow.
You will not go to the party. → I wish you would go to the party.
This last usage distinguishes wishes from conditional sentences. We would say, for example, “if it rains tomorrow …” to express a real condition in the future and “if it rained tomorrow …” to express an unreal condition (i.e. something that is unlikely to happen), but we would never say “if it will/would rain tomorrow …”.
By the way, if you haven’t read my guide on how to avoid the most common mistakes in English, make sure to check it out; it deals with similar topics.