My advice....

If you are actively losing weight, wait a bit for your weight to stabilize before you order a kilt. No sense in ordering a garment that won't fit you from the get-go.

On the other hand, if you are simply concerned that your weight will drop in the future, or "would like to" lose weight down the road, go ahead and order your kilt. It can be taken in if needs be to adjust for a smaller size, should that be necessary.

Worst case scenario, you can sell it and buy a new one in your size. But in the meantime you will have a nice kilt to wear!