Did Dumbledore have a plan for killing Voldemort?

Yes, he had a plan, but it was not always the same plan.

Dumbledore's first goal was always to eliminate Voldemort's Horcruxes, since he was well aware that, once these were destroyed, anyone could kill Voldemort, at least in theory. A Dark Lord who can be downed by a stray spell from an Auror is far less dangerous than one who can resurrected by his followers as many times as necessary. It is true that Voldemort and his Death Eaters fought the entire Ministry of Magic in the first war, and were winning, but the fact that Voldemort escaped unscathed from most of those battles was, if not really coincidence, certainly not an inevitability. We saw that three skilled magic-users could give him quite a hard time in Deathly Hallows. Dumbledore was, of course, aware of the diifficulty:

"Yes, I think so," said Dumbledore. "Without his Horcruxes, Voldemort will be a mortal man with a maimed and diminished soul. Never forget, though, that while his soul may be damaged beyond repair, his brain and his magical powers remain intact. It will take uncommon skill and power to kill a wizard like Voldemort even without his Horcruxes."

_{Harry Potter and the Half-Blood Prince}

I have no doubt that initially, he planned to try to kill Voldemort himself, once all the Horcruxes were eliminated.

‘You do not seek to kill me, Dumbledore?’ called Voldemort, his scarlet eyes narrowed over the top of the shield. ‘Above such brutality, are you?’

‘We both know that there are other ways of destroying a man, Tom,’ Dumbledore said calmly, continuing to walk towards Voldemort as though he had not a fear in the world, as though nothing had happened to interrupt his stroll up the hall. ‘Merely taking your life would not satisfy me, I admit –’

_{Harry Potter and the Order of the Phoenix}

Merely taking his life would not satisfy him, because he needs to destroy the Horcruxes first. However, whatever Voldemort says with regard to the nonlethal spell that Dumbledore used there, the latter is clearly not making much of an effort to avoid killing the former in the battle: he tries to suffocate him under a mass of water, wrap him in a rope of flame, and more. Besides, when Snape first betrayed Voldemort to Dumbledore, he was afraid that he would kill him, suggesting that he had been willing to use lethal force against the Death Eaters in the first war.

Dying was not on Dumbledore's to-do-list until near the beginning of the sixth book, when his carelessness with the Resurrection Stone left him with a debilitating and inevitably fatal curse. Naturally, Dumbledore himself, with the appropriate backup, would have had by far the best chance of defeating Voldemort once the Horcruxes were destroyed.

After Dumbledore contracted the curse, his original plan became untenable, so he moved onto another one. Perhaps the querent thought Dumbledore did not plan for Harry to survive, but that is incorrect. He did not plan for Harry to get the Elder Wand, but Harry's survival would have been assured by Voldemort having taken his blood:

“Precisely!” said Dumbledore. “He took your blood and rebuilt his living body with it! Your blood in his veins, Harry, Lily’s protection inside both of you! He tethered you to life while he lives!”

_{Harry Potter and the Deathly Hallows}

Dumbledore had known, or strongly suspected this, since the fourth book: that is why he had a "look of triumph" in his eyes when Harry explained to him that Voldemort had taken his blood.

Now, Dumbledore knew that Harry would survive, and he did believe that Harry had the power to take on Voldemort. Right after the first quote that I mentioned, Dumbledore says that Harry does have uncommon skill and power, particularly insofar as his ability to love provides him with a strong weapon against Voldemort—in fact, based on the way Dumbledore described his protection, it is possible that Voldemort or anyone else would have been incapable of killing him permanently as long as Voldemort was alive.

In addition, love is the basis of many other types of powerful magic, but even setting that aside, Harry is rather skilled at Defense Against the Dark Arts, by which I mean that he appears to be the best witch or wizard of his generation in that regard: he got an Outstanding when Hermione received an Exceeds Expectations, and his ability to produce a corporeal Patronus at 13 was little short of extraordinary. With more practice, he could have been a formidable opponent on the basis of skill alone.

In the end, though, I think there was some degree of desperation or hope in Dumbledore's plans near the end. He did not know for certain that anyone could kill Voldemort, not to mention defeat his Death Eaters, once all of his Horcruxes were destroyed, but he knew that they would at least have a chance. Eliminating Voldemort's immortality was the top priority.