As long as the shocks started leaking within the basic warranty mileage limit and you open a case with the dealer service department for the warranty work, it doesn't matter at all if the replacement shocks only come in after the truck rolls past the mileage limit. Thats Ram;s problem, not yours or the dealers!!!
More importantly, if you did not somehow misunderstand what the service manager was telling you, then that service department is either clueless or trying to play you and possibly even Ram.
That said, if they are genuinely unclear on how the manufacturers warranty works, then you will likely want to find another dealer with a better service department.
Even more seriously, If they are playing you AND Ram, in order to "double dip" (ie make you pay for the replacement shocks when they come in as well as charge Ram for the warranty work, then you definitely want to find another dealer AND let Ram know about what this particluar dealer is claiming cause the are trying to cheat you and/or Ram ... intentionally or not.
Just my .02