If your apartment is rent-regulated and your landlord converts your building to a co-op or condo under an eviction plan, you have a three-year window of continued occupancy as a non-buyer. It begins on the date the NY State Department of Law approves the conversion. If your lease expires before then, the landlord is obligated to renew your lease for up to the three years. If your lease extends beyond this three-year time frame, it must be honored through its termination date.
After that, you'll have to find another place to live, if the landlord doesn't want to continue to renew...unless you're a senior citizen or disabled. Eviction plans do not terminate renewal rights of seniors or disabled individuals. Depending on the other factors involved, it may be a good idea to notify the landlord in writing if you are eligible to retain your leasehold because of age or disability. Pointing this out early on supports your position, so the landlord cannot later claim that you're raising a last minute, unsubstantiated defense.
Even with a disability though, there's no such thing as a guaranteed result in court. Also, the legal definition and scope of disability for a housing case may be different from requirements for other purposes, such as obtaining various government benefits.
One other factor that can sometimes enter the mix is a shift in the ownership of the co-op shares assigned to your apartment. In that instance, the owner of the shares becomes your new landlord. Needless to say, one landlord's behavior can be different from another's. The new owner may be more aggressive in pursuing litigation against you to obtain control of the unit, or may afford greater leniency in allowing you to stay.
In whatever scenario confronts you, it's generally best to document your rights. However, be sure to speak to a knowledgeable Tenants' attorney before putting anything in writing.