No, not really. The Legend of Zelda isn't the kind of series to be capable of supporting a bunch of spin-offs like Mario can. It's just that not every franchise can have smaller branches such as MarioKart and MarioParty without "ruining" it.
Wait...I think that Zelda Series is already more populair then the Mario Series. I think most gamers out there would buy a nintendo console just for Zelda rather then Mario.
Just because Mario is the main mascot and just because mario gets more advertisement, does not mean its more populair.
Example: Check this poll results on IGN
Heck yeah. People always call Nintendo "kiddie" and it always makes me mad. It isn't true. People think that because Mario is the face of Nintendo. If Link were to become the face of Nintendo, that would change. So yes.
^I disagree on some levels, since i go to school or wherever and i wear my zelda shirt, and everyone comes up to me and says: what is that? but people who've played both tell me that zelda's way better, or they've only seen it in SSBB/SSBM/SSB
It kinda already is. At least in the eyes of a gamer. Mario has more abilities to branch out into different kinds of games, such as sports, which is something Zelda will never have. However, Zelda is always more anticipated than Mario, which makes it more popular in a few different ways. To the general public, Mario is definitely more popular, but gaming-wise, Zelda has the upper hand.