Verified answer

lol No they could just cry their trainer back to life.

But seriously, If the trainer died while they were traveling in some desolate forest the Pokemon would probably be stuck in the Pokeballs. Although lots of Pokemon are shown coming out of their pokeballs without their masters permission, so they could probably break out and I guess just go back to the wild.

If the trainer died in a city, someone would probably find the Pokemon eventually and either take them in or let them go.

I'm pretty sure that Ash found a ghost pokemon that was trapped in an underwater sub or something, and it was stuck in its pokeball. So they're like.. in limbo, I guess.

Someone would come buy and find them dead and release all the Pokemon. The ones that don't want to go will be probably be pushed onto family and friends.

yes, unless they were killed by the death note. In which case, krillin, naruto and some guys from one piece go on a quest for the talent of blank.

its set free or contained inside its pokeball