League is not gonna die EVER I Promise. if u consider the games with no more updates anymore that still has tones of players like warcraft 3 ,league of legends will have some fans forever and i would say that it will live way longer than dota2 because of the constant changes(jeremy said) and creative advertising style that it has like KFC deal in china(google it ) and free all skin all champs in pc bangs in korea and some other referral award which been before (if it drops in fans one day maybe referral program reappear) but if one day the amount of players become way less the game still lives
Here is why Riot games has no Servers by it self. its all hosted on amazon AWS this service provides very very good features such as u pay for what you use so if 100 million players play they pay for 100 million if 1 million players stay they just need to pay for those 1 million players the only thing that cause Riot games to lose money is probably their employees or they need to stop some servers with low profit (i would say that japan server is one of them for sure )
and finally u should know this riot games is a billion dollar company even without profit they can live for years and they backed up by their owner too (Tencent Games - which is a 500+ billion dollar company) .
So in conclusion They are way smarter than dying over night and if league of legends project will stops one day surely riot games come with a better game