Exchanges make money off you via exchange fees. If they hold your withdrawal pending for days end, it's most probably because of technical issues. Can they run low on funds where they cant honor it? It's probably possible, but there's no way to know for sure unless you have insider information.
Mind telling us what exchange you're using?
https://www.facebook.com/pg/bitsane/community/?ref=page_internalLOT of people are stuck and very little communication and no support tickets are being answered.
I have been stuck with XRP for 6 days, and down 50% and whipped away all last 2 months profit. Not a small amount either.