I agree there is a market for *some* previously unreleased material for many artists, dependent upon many variables (ie, condition of masters, popularity of the artists, current stage of nostalgia revival 1 & revival 2 consumers are in, etc).
As to whether releases can "survive" the current marketplace for reissues of old folk revival CDs, I think is also highly subjective, as is what constitutes economic viability for reissues. It is a damn fickle business, and once the initial PR surrounding a release dies down, so do sales, particular of artists who are deceased, or otherwise unable or unwilling to promote the CDs.
As has been said previously, the amount of money isn't very considerable for any of these reissues at the end of the day. Unless of course you can create a controversy to keep an artist/CD in the news, which is what I think has been the case with the Mollie Music releases. The amount of inspirational cripple stories that have been recently been written about Nic Jones are more than a sick parody at this point, IMO. As was the CD cover. I know--it was supposed to be funny.