Ten pounds to go...when to buy new clothes

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Most of my clothes are from about 50 lbs ago. I still want to lose about ten pounds but that will probably take AT LEAST another two months. My question is: how much of a size difference does 10 pounds make? Im trying to decide if I should buy some clothes now or wait. I've found a couple of size 4 pieces that look great except for the length. I just don't want to spend additional money getting them hemmed only to find they don't fit later. Those were dress slacks, which I really need for work.

I'm considering getting my old slacks from last year altered, but does anyone know if a size 16 can be taken in to a 4/6 without losing its shape? Will it be more cost-effective to just buy new pants?

Thanks!