There are old people in Pokemon but I have never seen any old Pokemon. Do Pokemon age and die? Also, if they get hurt too much, will they die of wounds? Have there been any deaths so far?
Pokemon could die in multiple ways, some of which are listed here:
By Over Exertion: In the Movie, Celebi: Voice of the Forest, it is shown that a celebi goes out of control, wreaking havoc in the forest. It exerts itself so much that when it calms down it simply disintegrates and dies.
By Sacrificing Themselves: It is seen in the movie, Pokemon Heroes, that a Latios sacrifices itself to protect the city of Alto Mare. How exactly does he die is unknown.
By Getting Eaten: The pokedex entry for Wurmple states that it has to defend against Starly to prevent being eaten. We can assume that the same applies for Caterpie and other worms.
Some Special Condition: Like Charmander, who will die if the flame on his tail goes out. This is also valid for its evolutions.
Aging: Pokemon who do not die from the above causes can be assumed to die from aging. This assumption is validated by the existence of pokemon graveyards with the people visiting it remarking on the long companionship provided by pokemon.
Some anomalies which are unexplained:
Existence of Legendary Pokemon: It is probable that legendary pokemon live forever. Pokemon like Groudon, Kyogre, Rayquaza are referred to as "super ancient pokemon" implying that they live forever. Same may be the case with other legendaries.
Ghost Pokemon: Deaths of pokemon do not explain ghost-type pokemon. It is possible that they are born as ghosts. Pokemon after dying may become spirits, like the Marowak killed by team rocket.
In essence, the aspect of pokemon death may have been avoided in the franchise because it was designed primarily for children.
REFERENCE: How do Pokemon die? on Quora