Not if you're still making money off of the work. But if you're not making money off of it, it's an incentive to let the copyright expire. Corporations might sit on things that they're not making money off of in order to try to make money off of them later, but they'd be limited to 50 years, which is a vast improvement.

Only for "non-profitable" works. It is a downside in the tradeoff. But even then the escalating price for extensions should offer an incentive to limit what works fall into this category and subsidize society when they do.

We are not just balancing the individual creators vs corporations, but also creators of derived works, and societies benefit at-large of more creative works in general. We want to maintain and compensate creators "enough" to maintain incentives for creation, but otherwise maximize the commons.