So, your options are really keep using your iPad 3 or purchase a new iPad if you feel you need or want to. Your iPad 3 is NOT, suddenly, becoming obsolete or useless. Your iPad 3 will still do everything it does now and you will, get, at least, another full year, perhaps two, if you decide you want to wait longer to get a new or newer iPad model.
You have had four years of iOS upgrades and updates. Your iPad 3 will work as it always has and the apps you have installed on it will continue to update and receive some level of app updates relevent to your current iOS. Just because your iPad 3 is no longer able to upgrade to the latest iOS doesn't mean your iPad 3 is suddenly useless.
