No one can answer that as each case is individual based on what the company does or can do. Right now PDX Partners (and the other two) needs to get a Market Maker willing to submit a 15c211 or Form 211 to return to pink trading which can take weeks to years (difficult getting an MM to do it)... think the time element is the reason traders/investors eventually get tired and pull out... the one important thing is to have the funds to get this done if a company feels it's been wronged and it truly has a business.
And btw, there are lots of companies on the gray market by choice to go 'public' and they're doing well... there are also some that were relegated or 'demoted' from pinks to the gray (many of these just don't have the major money to get off and some of course may truly be 'scams').