You can always buy stuff later when you need it, but if you buy stuff now that's too big by the time you need it, it's a waste of money.

So, i think it depends on 2 things
1) do you need them now where you live, or is it warm enough to ride with arm warmers, leg warmers and a vest & jacket?
2) if you don't need them now, by the time next winter rolls around, do you think you will have lost enough weight to need a different size?

If you plan on a big weight loss by next winter, I'd go with arm/leg warmers instead of the expensive long sleeve/long leg clothes, as it's likely your arm/knee/leg warmer size won't change- and even if it does, those too-big warmers can become an outer layer when you want to wear two sets of warmers.

If it's cold where you live now, will be cold for another month and you are planning on riding, buy the sale stuff.