Although it is hard to predict what will happen in a particular area in a few days, smoke from distant fires tends to accumulate at lower altitudes and move around depending on the wind direction. The extent of pollution can also vary dramatically during each 24 hour cycle - it is not uncommon when affected areas are relatively clear early in a day, when the winds are calm, but get polluted in afternoons. My strategy for long distance mountain hikes when the smoke is a concern is to sleep high (above 10k) and cover the lower sections (valleys ect) as early as possible. This may not be particularly useful for you, but I would still not cancel until the last minute since there are currently no significant fires near the Whitney zone. Here are examples of how quickly things can change:
1) I hiked the JMT Northbound in August of 2015 when the fires were pretty bad, prompting people to bail and some even ended up going to hospitals due to smoke inhalation. In several instances, the Southbound folks were describing specific spots as terrible. I was reaching these spots less than 24 hours later and they were ok. Smelly but clear.
2) Last year, we cancelled the group trip to the Garnet lake area because PurpleAir and Mammoth webcams were consistently showing terrible pollution. We cancelled less than three days before departure and then learned that the whole area got cleared on the days of our planned trip.
Good luck. I hope your trip works out!
