None of these sentences expresses what you define in your last paragraph: “wickets will keep falling inevitably no matter how much one tries to stop it.”
The problem does not lie with the tense but with the conditional construction. “If they HAVE† to” implies that there is some doubt as to whether they have to keep falling, which is exactly the opposite of what you are trying to say. What you appear to mean is this:
Wickets will keep falling—they have to!
But I do not think the HAVE to construction is your best choice. It seems to me you’re not talking about a physical obligation (much less a moral or legal one) on the wickets, but about a ‘fact of life’, or at least a fact of the game. I would write:
Wickets will keep falling. They always do.
If somehow you do mean to use a conditional—that if wickets are obliged to fall they will do so—your use of non-past-form will in your consequence clause requires you to use non-past-form have to, as in your 3d sentence.
If wickets have to, they will keep falling. or Wickets will keep falling if they have to.
In the even more unlikely event that you intend an ‘irrealis’ (unreal, counterfactual) conditional—that wickets are not obliged to fall—you must translate both clauses into the past form:
If wickets had to, they would keep falling. or Wickets would keep falling if they had to.
This might also be expressed (grammatically but awkwardly) as:
If wickets were to have to, they would keep falling. or Wickets would keep falling if they were to have to.
† The infinitive form of a verb written in italicized capitals means “the form of this verb appropriate to the specific context”.