The Taiwanese government would have to negotiate those terms with the mainland before any such referendum could happen. However, that’s unlikely to occur in the near term if the DPP, which is the “pro independence” party, wins the upcoming presidential elections. When combined, parties interested in negotiating with the mainland are polling higher than them. However, the DPP maintains a a slight lead with a plurality of support. Needless to say it’s a complicated situation. I doubt the issue of Taiwan’s future will be resolved anytime soon.