There is always a time for RPGs, but that's just not realistic. Frankly, casual games dominate right now, not shooters. Party games, simulation games, training games, these rule the industry. And if that ever changes, what else could it be?
Fighters are absolutely impossible, because 10 million or more people are never going to want to play a fighting game without Mario in it. RPGs are possible if ones made in the west grow to a truly large level.
Platformers have been slowly declining in each generation. In the NES era, they were practically the only games that sold. During the SNES era, gaming opened up. Fighters and RPGs started to make way, and platformers saw a dip in popularity. The trend actually reversed itself in the fifth generation, but then continued in the 6th generation. Now we're at the 7th generation, and platformers have little influence outside of Mario. Unless the genre is opened up again with new competitors, it will never truly dominate.
If casual games (which are split into many different genres) aren't the future, then I'm going to say peripheral based games. People are finally starting to bring arcades into their homes, even if they're not realizing it.
There's no denying this future. Look at the sales of games like Guitar Hero, Rock Band, Link's Crossbow Training or other Wii-Zapper games (House of the Dead 2 & 3 Return and Ghost Squad), Wii Fit, Mario Kart Wii.
You can not disagree with this logic.
