Lot's of options: OTCBB, AMEX/NYSE; Toronto; London; something in Asia/India might make sense.
They could just stay on the pinks for awhile, and they may have to, and work their way up the pink listing ladder in preparation for a move.
Easy enough to look up requirements for other exchanges. As a side note, the US used to be a leader in IPO's, but I believe that is no longer the case, mainly due to Sarb-Ox and other regulatory requirements. As a result, US has lost out on tons of business and tax-revenue. That is usually the result when Congress over-reacts to a problem. The media builds up a furor and then Congress 'fixes' a problem by using a bat instead of a scalpel. End result: unintended consequences make things worse off, business leaves US.