It's more than a wish, Homer. Although a lot of reconciliationists are Calvinists and think they have to be in order to uphold universal reconciliation, this is just not the case.If, as you insist, open theism is correct, then you can not possibly know, nor can God, that all will eventually repent in hell. They may only become more hardened. Hasn't happened yet so it must be unknowable and only a wish.
Because the future cannot be known, you are technically correct in saying that it cannot be known that all will eventually repent. But practically, you are incorrect. Indeed, the probability that some (or even one) will hold out forever is close to zero (if not zero).
Please reconsider the analogy of tossing a thousand coins on a large area of special sticky fly paper enclosed in a wooden frame . The analogy is far from perfect, since coins are not free-will agents. Nevertheless, I think the analogy has some merit. This special fly paper has the property of always sticking to the tails side of the coins, but never to the heads. Let's say we want all of the coins to eventually turn up as heads. Throw the coins onto the fly paper. We would expect about half of them to turn up heads and the other half tails. But of course, it could happen that 75% of them (or even more) turn up tails. In any case, if we move the frame up in such a manner as to toss the coins again, those which turned up heads will stay stuck to the fly paper, while the rest are tossed again. Now we would expect a number of the newly-tossed coins to turn up as heads also. But even if ALL of them turned up tails, we keep on tossing.
We toss as long as any coins turn up tails. It seems obvious that we can "know" in some sense, that all of the coins will eventually turn up heads, even though the tossing of coins is a future event. Of course, theoretically, we could toss the coins for a week, or a year, or 10 years, and there could still be some coins turn up tails. But would anyone bet on it even if the odds were 1000 to 1? I don't think so. However, it is possible that some could continue to turn up as tails for 10 years, or even a life time. But what if some immortal creature had forever to toss the coins. Surely they would eventually all be heads up! It is still conceptually possible that they never would throughout eternity, but practically it would be impossible.
So if God works on the lost in hell for ages of ages, not only through tough disciplinary measures, but through sending His perfected saints to minister to them, does it seem possible that any could hold out forever?
As in the case of the coins, it is conceptually possible, but not practically possible.
This is why I am able to believe, and confidently assert that all will be reconciled to God. It's much, much, more than wishful thinking! Of course, you are right that technically, I cannot know this to be the case.