A deal has been done about a non-issue that stirred up national sentiments in Iran. The West does not lose anything here because the entire threat of an Iranian nuclear weapons program was due to irrational paranoia. The Iranian conservatives, on the other hand, will lose a lot of their political power due to this deal. Their argument (that most Iranians accept, however pro-Western and anti establishment they are) is that the West had improperly tried to coerce Iran into giving up their peaceful nuclear program.
If it is accepted as a fact in a country that foreign powers want to improperly impose their will on that country on a certain point, then the liberals arguing for better ties with those foreign countries will have a hard time putting forward their argument. It totally weakens the political base of the liberals, as the conservatives are seen to be correct.
In Iran, however, there was also another force at work. The sanctions made Iranians think again about the way they were arguing their case. That led to a more moderate president being elected. The fact that he did succeed to negotiate a deal with the West is a huge boost for the moderate and liberals in Iran (note that while Russia and China were also part of the negotiations, to them the Iranian nuclear issue was never a problem, this was only ever a dispute between Iran and the West plus its Arab allies).
What will likely happen in 15 years from now? What we're likely to see is an Iran where the people enjoy a lot more political freedoms. The economy will have improved lot. Western companies will have invested a lot in the Iranian oil and gas industry. Iran's nuclear program will only make news headlines if Western companies get involved in the Iranian nuclear industry. That may well happen as the World needs to make huge investments in the nuclear sector to deal with the threat posed by climate change. We may well see the West changing the deal with Iran about the Arak reactor, because in the future we do need to produce large amounts of plutonium.
The whole problem with nuclear energy is that if you only use U-235 then using nuclear energy to providing the World with all of its current requirement for energy, would cause all the known uranium reserves to be used up in a century. However, if you use nuclear reactions to convert U-238 into PU-239 and use Th-232 to produce U-233 which is also fissile (using so-called fast breeder reactors), then the known reserves will last 30,000 years.
In summary, the West suffers from WMD-o-phobia, Iranophobia and Radiophobia, which has caused a lot of damage to the environment, the World economy, and the political situation in the Mid East. The negotiations with Iran and the deal that has been agreed to will have contributed a lot toward the West coming to terms with these issues, the World will be a lot better off as a result.