I would say that you should take this as an opportunity to build your wardrobe thoughtfully (somewhat a la the capsule idea). Pick a neutral you want to work with - black, gray, brown, navy - and a couple of colors that are flattering on you and slowly fill in the blanks with those. That way they'll coordinate with each other and possibly with some of the things you're getting too small for unless you've decided to radically change your style. Also, in tops and dresses, look for empire waists since they'll be more forgiving of both weight fluctuations and tiny people. If you carry weight low, like I do, wide-leg trousers can also be handy for masking some weight gain.
As for saving things, I wouldn't do a full clean-sweep just yet. Definitely get rid of anything that was just filler in your wardrobe, but hang on to some of the things you liked. If the changes seem to stick, dresses and skirts can often be altered with minimal fuss, so that's something to keep in mind, especially if you already have some special occasion wear, which would be annoying to have to replace. If the changes don't stick, you'll have to replace a few things, but again, you won't be desperate for clothes and can take your time making good choices.
Congratulations on the weight loss!