Happiness, rebirth, and the death of an arahant I am new to Buddhism and have a question I am hoping someone can answer.

My understanding is that realizing enlightenment is universally desirable. In other words, it is considered “better” to realize enlightenment than to not (i.e. if a genie ever offered to magically grant someone the realization of enlightenment, no one should say “no”).

When it comes to what happens to arahant after death, my understanding is that Buddha did not give a very concrete answer. I've read a couple of answers such as, "it falls under the category of things that are not known" or "the answer will not end suffering so it is irrelevant” or “arahant are extinguished like a flame”, etc. He did seem to concretely say, however, that arahant are definitely “freed” from the cycle of death and rebirth. And when it comes to what happens to non-arahant after death, he seemed to have a very concrete answer with no hesitation: they/we die and are reborn in an endless cycle of dukkha (suffering).

My understanding is that both happiness and sadness are dukkha (suffering/impermanence). But isn’t happiness generally considered a pleasant feeling? And aren’t some non-arahant more happy than they are sad in life? I’m not saying I’m one of those people, but don’t those people exist? So for them, perhaps an endless cycle of death and rebirth isn’t that bad? Life can be net-positive in happiness for some, can’t it? For those people, does it make sense to exit out of this endless cycle of mostly-pleasant life and instead enter....nothingness? The unknown? Become an extinguished flame?

I have read that arahant experience “happiness” in an unfathomable way, far beyond the happiness of the laymen. Even if that is true, that “happiness” is only guaranteed for the rest of their current life is it not? After that, even the Buddha is not sure what will happen except that they will for sure not be reborn to experience that happiness again in the next life because they will have been freed from the cycle.

If it was just laid out as, “following the eight-fold path will end your suffering in this life” then that would be simple. But then there’s also that added bonus of “if you realize enlightenment, the illusion of ‘you’ will forever be nothing.” But what if I’m not suffering all that much? What if I have a pretty peaceful, happy life? Does it make sense for me to say “yes” to that genie?

Thank you in advance.
Your question seems very sensible. Some thoughts... 

I think you're wrong to suggest that the Buddha was 'not sure what will happen...'. There are some things that may be known but not explained. He advises us not to worry about metaphysical problems and just take the medicine, but this does not mean these problems are not understood or the facts not known. 

If you are having a pleasant time, as you say, then you may not feel you are suffering and you may question the need for the medicine and have little motivation to take it. The Buddha was in this position early on but saw the suffering of others and recognised his own future death and suffering. His medicine is not just a cure for suffering now but forever, and while you may feel free of suffering right now this situation is not going to last. (Sorry about that).            

Thus it is said that the Gods have such a cushy time they may lose their motivation to push on to full attainment, but in the end even they must give up the pleasant life and sink back into the mundane, making it more helpful to be a human being with the motivation to go all the way.   

I doubt your pleasant situation will hold you back since it won't last for long. What you call happiness is not what the arahant means by the word. His or her happiness is unshakable and not dependent on conditions. When you are happy in a way you know nobody and nothing can diminish or destroy then you're properly happy. Usually our happiness can be destroyed instantly by a death in the family, an illness or even just a missed meal. Happiness is real happiness when it is permanent, at which point the word 'happiness' may become slightly misleading as a description. 

It's a slippery and subtle doctrine and these issue take some time to sort out, and they cannot be properly sorted out without some 'empirical' evidence to inform the process. 

Needless to say this is just some thoughts, not advice from a guru.