Bitcoin isn't the only option. We've already seen that when the price of Bitcoin dips miners flip over to whatever cryptocoin seems next to bubble, seems next most interesting. Certainly what is called Bitcoin itself (today) has "hard" "deflationary" "caps", but as soon as miners get bored with that, there's always more room for more forks and other coins.

Even if Bitcoin isn't intended to be "growing forever", the ecosystem can and will.