see, the problem with nuclear disarmament is that with the exception of America, Russia and maybe China, most nuclear nations have weapons for more regional political reasons. Britain, France, Israel, India, Pakistan, North Korea, these nations, regardless of how many individual weapons they have, don't have the infrastructure to engage in nuclear war at anything close the the strategic capacity that Russia or America have. Iran, for as much as a nuke might be a way to keep America or Israel from performing military operations against them, rather allows Iran to extend its influence by taking that option off the table.
I guess I shouldn't say it plays not military strategic role, just more that, by having a nuclear weapon, you can extend your regional political power essentially without fear of reprisal. America's continuing war in Pakistan, however, shows this might not be entirely true, but those are weird circumstances. I'd just say, most nuclear armed nations, or nations that want nukes, have them for reasons besides engaging in nuclear warfare,
For real disarmament then, that political reality would be taken off the table. And sure, we can talk about space weapons or whatever, but compared to the North Korean or even French/British nuclear military capacity, both America and Russia might as well be space weapons. The degree to which America/Russia have first strike, 2nd strike, survivability, automaticity, etc built into their nuclear strategic planning is unlike anything else on the planet. Nuke or not, the military battlefield isn't leveled between America and Iran, even if they did have a delivery system that could reach America.
The only thing that would make nuclear weapons, as they exist today (ie: as large missiles/bombs with huge payloads), obsolete would be a 100% effective missile shield that applied equally to all nations (even then, traditional bombs would still be relevant in geopolitics). Even if there were simply just "more-powerful-than-nuke" type weapons, the destructive power of nuclear bombs will probably make that technology a part of military arsenals for a long time.