If casual becomes the way of gaming then there will be a market crash like in '82(i think) because the devs will get lazy the consoles each gen wont have any features over the previous gen and the Greatest Franchise of All Time i.eMario,Zelda,Metroid,FinalFantasy,possibly DragonQuest and so on will die out because the fans of the series will be washed away in the rush of casuals and devs switching over to casual games and not even Nintendo could save the industry then it would take alot to bring it out of a so called 'dark age' like that.I dont think Mario would die but Zelda and Metroid would they are alot more hardcore than Mario is.FinalFantasy and DragonQuest would die out and so S-E would die out because their fans would again be washed away in the midst of casuals and eventually: Namco,Tecmo,Konami,Koei,Atari,SEGA,Midway,Epic,Ubi,FreeRadical,InfintyWard,Activision,Insomniac,NaughtyDog
All the great developers we know today would die out and so what would we be left with EA,ooo score, and EA arent even good developers.If only the Wii and DS could just stop selling as fast but still be profitable for Nintendo because these consoles aiming at casuals(whether they are picking them up we dont know)are making devs switch to casual games which leads to a 'dark age' of gaming and thats not good for anyone.
Again worst scenario but its still very much possible.
Don't worry about this scenario, it has a 0 % chance of becoming real.
What would come closer to a crash is if there was no Wii and just the 360 and PS3. An industry full of $20+m productions for consoles which don't have the userbases to support all these games, this could cause the industry to crash in the long term.