According to this Radio Liberty article:
"The Ukrainian government still has much to do to convince its people of the advantages of joining NATO. But the percentage of Ukrainians favoring membership has doubled over the last three years, reaching 36 percent. However, 28 percent remain opposed to membership and the other third are undecided."
If even half of this 36% of undecided Ukrainians can be convinced by the pro-NATO side, then Ukraine will be in NATO, sooner rather than later. All that's necessary is for another 15% of Ukrainians to go from undecided to supportive.