I consider the separation between Artesh and Sepah a strength. Iran is a mountain fortress that is incredibly hard to invade. Which also means that Iran's first line of defence is outside its borders. Therefore, having a conventional military to protect Iran proper, and an asymmetric military to fight Iran's enemies abroad, makes sense.

Sepah has increased its military strength and capabilities over the years. Its economic and political influence have also grown exponentially. However, it will always be bound by its size. And so by numbers alone, it will not become more "powerful" than Artesh, at least not militarily (although Sepah does control Iran's missile programme, and has huge sway over its nuclear programme).

I sincerely doubt that Sepah and Artesh will merge in the future. There is no military reason, and their doctrines are not reconcilable.

Across Iran as a whole, the new generation is less indoctrinated. Ironically, the Islamic Republic has resulted in a far better educated, wealthier, and modern society. But Sepah and Basij are Sepah and Basij, and they will always maintain a core constituency of ideologically driven followers. More broadly speaking, Iranians across the board are nationalistic, so if they don't join the military for religious purposes, they will join for nationalistic purposes.

The Islamic Republic is wise on a tactical level: it is quick to adapt to changing circumstances. But it is weak on a strategic level: it does not possess the strategic foresight to understand and shape discourse. It is reactive. Just look at Iran's previous presidents: they almost directly reflect American presidents. Clinton 1993, Khatami 1997. Bush 2003, Ahmadinejad 2005. Obama 2009, Rouhani 2013. Why? Because whatever America does has a direct consequence on Iran's security. Therefore the Islamic Republic adapts. It's the same story domestically.