To be honest remember back during the SNES. People would have asked , could Nintendo survive without Donkey Kong. Today Nintendo is alive and well and Donkey Kong is all but gone. I think if Nintendo lost Mario they would double back and build a replacement franchise. Yes Pokemon would be a big one but Nintendo could easily survive off of the Wii franchise, or Animal Crossing , Pikmin , StarFox, DonkeyKong, Zelda , Metroid.
Sure none of those franchises are the heavy weight Mario is but with Mario gone I'm sure one of them would quickly take his place! Infact I think Nintendo knows it can't fully rely on Mario, just think Mario wasn't even present at the launch of the Wii and won't likely be present at the launch of Nintendo's next console!
-JC7
"In God We Trust - In Games We Play " - Joel Reimer