What is the latest to wait to tailor dress?

Hiya! My wedding is October 10th and I have a dress that fits me beautifully.

The semi issue now is that I'm back on Zepbound, and the weight is dropping. I estimate that I can lose 20 pounds and still not need to tailor the dress, just based on the corset and previously being at that size. However, what if I have to tailor the dress? What is the latest that you could wait for that scenario?