Water heater tank - the upper of burner is rusty - will it leak soon?
Water Heaters that you can purchase today usually have a warranty from the manufacturer. I think the average warranty is about 6-8 years. You can find ones for 8-12 years, but you will pay much more.
You can estimate fairly accurately the life-span of a water heater by looking at the warranty. This is not always true, but it's a good way to get reasonable life-span.
I believe any water heater that makes it past the 10-12 year mark is close to replacement. There are the rare ones such as your's, that should be included in the Guinness Book of Records. And although you may get some more years of service out of it you would be wise to start considering a replacement.
Looking at your photo the rust means that water has already leaked on the bottom. There is also sign's of pitted metal which means the water has been there for awhile. If it's not leaking alot now than it will be in the near future.
Yes. It's time for a new water heater.