Change your plans from what, to what?
The whale watch vendors don't usually start their specific whale watch cruises until early December. However, many of them do snorkel trips and you might see some whales while on those trips.
The whales have been coming earlier and earlier. However, it is not in large numbers, so yes, your chances of seeing whales the next few weeks are definitely slimmer than in the December through March normal season. The numbers of whales in the area in the "season" is probably in the thousands, and the vendors do truly guarantee sightings. We have whale watched in season about 20 times...never went without seeing whales. Nowhere near those numbers now.
Maui is the better area for whale watching, off Lahaina, or out of Ma'alaea Harbor, which is the closer area to where POA docks. Kona isn't bad, but its usually rougher there, and not as many whales as Lahaina area.