Void sales contracts: Statute of limitations questions

I’m looking for some perspective and advice here, and I appreciate any insight you can offer. This is a bit of a legal knot, to be honest. Back in 1993, a purchase agreement was signed for a 50% stake in a local tavern. The buyer registered the deed properly. For years, a third party occupied that portion, operating under a verbal agreement with the buyer that they could step outside whenever necessary. Well, that third party passed away, and now their heirs are refusing to clear out the property or hand over possession. We kicked off a lawsuit to regain possession back in 2006, and it’s been an uphill battle ever since. We initially won at the trial court level, but the heirs appealed, sending us right back to square one. Then, the trial court issued a second ruling in *their* favor. We appealed that, but the appellate court upheld the decision, essentially claiming the seller never had the legal standing to sell that half-share in the first place, rendering the 1993 contract null and void. We’ve requested a judicial review and filed a petition with the Supreme Court, so the whole mess is still pending.
My question is this: do we have grounds to sue the seller for damages? Even though the contract from 1993 was declared void, that determination didn't actually happen until November 2012, when the appellate court handed down its ruling.
Thanks again for your help!