I have done this twice in the past year.
First time, just by chance, did my first
DVC tour end of April, which happened to be just before the start of a new incentive period. Incentives weren't better, so just moved forward with the prior period incentives.
Second, time, did my "tour" just before the start of new incentives in July. Again, new incentives weren't better, so just locked in the prior period incentives. Then, in mid-August, well after my 10-day rescission period, "welcome home week" incentives were unexpectedly released which were better than what I had locked in (by about $1,100). While I was past my 10-day rescission period, I had not closed. I e-mailed my guide, and said I'd like the new incentives if possible, and it was done - just had to resign the paperwork. I don't think they're obligated to do this, but my understanding is that they generally do.
Incentives rarely get better form one period to the next, but it can happen, particularly at certain point levels. I think a more important factor is your UY and/or whether you're taking advantage of magical beginnings - for this current round of incentives, if your UY (or desired UY) was December, I think I'd much rather lock in current incentives and take advantage of magical beginnings than be worried about which period will have the better incentives. Now, if your UY was something else, might do my "tour" leading up to the December 10th, and then decide after you see each period's incentives.