There is no way the price of bitcoin will not affect signature campaigns as most campaigns don't have the fund in hand before now so it becomes that expensive to run. Aside that, because of the fact that the market is so decentralized, the fee to be paid will hardly be uniform and that is another thing affecting the whole issue because when a campaign comes with an amount different from the average obtainable, only few people will show interest with the hope that higher paying ones will be out very soon.

I think the way out is where managers will fix the amount in fiat value to be paid in BTC as at the time of payment but that will also have its own disadvantages at the time of crashing prices because they will then have to pay more in BTC value.