If the Bitcoin network is valuable to someone, they would likely invest to keep it running and secure. I would be more than willing to pay to run my mining equipment (bought with previously-mined bitcoins, about $1/day to run) to keep the network up.

Speculation has driven the cost of mining way up, but the speculation isn't inherent to mining. If the network was run entirely on a "charity" basis, the costs to mine would be much, much lower.