1. If your grandfather died intestate ( without executing a WILL ), then your grandmother (if alive), their children ( both sons & daughters ) are entitled to equal share in the property.
2. Other legal heirs of your grandfather can file a suit for partition, declaration and separate possession of the property by metes and bounds immediately or later after the uncle gets registered on uncle's name. However it's in the best interest of other legal heirs to file the suit immediately before the property is registered in your uncle's name solely.
3. Under the limitation act, the leftover legal heirs can file a suit after two to three years but since the matter is time sensitive, better to file a suit immediately without any loss of time. To initiate, let the other legal heirs send a legal notice through a Lawyer to your uncle, before filling a suit.
4. The jury will decide on the merits of the case and may order for partition of the property by metes and bounds equally to all the legal heirs, including your uncle.