When the SNES patents will expire?

In 2015 , 25 years have passed since the release of the SNES. The system is only protected by patents , right? So when all the patents are expired will be legal to make your own SNES clone?
Im thinking about possible homebrew SNES clones , and guides for making your own one more than in commercial clones
Obviously , I understand that trademarks and IP are a different subject( you cant use the name "Super Nintendo" , the firmware of the spc700 , etc..)
There will be a day in which the snes will be free? Or there is an intricate legal system that prevents the hardware from being free, even when all the patents are expired ?

P.D: The 6502 and The 65816 are still patented?

The SPC700 IPL probably has a "thin" copyright, especially given the US Supreme Court's ruling about the Toner Loading Program in Lexmark v. Static Control Components. Because programs can and do JMP into the middle of it, a single byte difference in the length of a routine is enough to cause programs not to work. So it can be argued that copying the whole thing is a fair use for interoperability purposes. But as usual, call your lawyer before manufacturing anything.

As for the 6502 and 65816, patents still last 20 years, and exclusive rights in the integrated circuit layout itself (the "mask work" in US parlance) last 10 years.

6502 is from 1975 and the 65816 is from 1983.
I dont know exactly the date of the patents and the mask work but the patents that are older than 1995 should be expired by now , right?

Probably the likelihood of one surviving a lawsuit from Nintendo (regardless of the outcome) would matter a lot more here.