I hear people saying they think Bitcoin will be worth nothing once it is all mined up. (but wouldn't that just make it harder to get and drive up demand)
Not really sure, but figured I would start a poll to get users input. Thanks!
That all really depends on how the coin is setup to run. There's plenty of examples of cryptocurrencies that are not minable, but are still profitable (e.g. IOTA where your txfee is authenticating other transactions, effectively making the "miners" the people doing transactions, and there will always be 2x verifications for each transaction made).
So no, mining is not essential to a coins longevity. And no, I personally do not believe that Bitcoin will tank when the supply runs out. There's plenty of examples of coins that support their network without having miners.