If you wait this long to express an attack of your patent then you don't deserve the patent. The idea behind a patent is to allow the inventor time to build his market and prevent unfair market dilution.
You can't allow a market to grow without your input and then claim ownership 3 years later, you deserve to be screwed over. Look after your rights from day 1, not when it starts making money and now when you want a cut with out any effort.