This is a very rough estimate:

On Kryptonia.io, no one is selling SUP options for less than US$0.01/SUP right now.

There are 300 million SUP pre-mined (100 million was ICOed and most of the remaining 200 million is locked, releasing only about 900k per month).
There are about 57700 blocks, with block reward of 560 SUP = another 32.3 million SUP.

So 332.3 million total SUP * US$0.01/SUP = US$3.32 million market cap.

I think it will grow if dev is correct that two Honduran companies are partnering with SUP; once those partners are actually accepting SUP the value will only go up.  The US$0.01 price probably reflects some uncertainty about when that will happen, and what it will look like.