Which is better, unlimited "battery" or a 40 hour battery? It may not be a big issue for you, but for me that's a very significant tradeoff. And I haven't looked into studies but I have personally done multiple side by side comparisons of the same headphones/speakers connected via bluetooth vs wired and have yet to find a set where I was not able to notice a difference in the sound quality. For me, that's enough, but I'd encourage you to try it out yourself or seek out some studies (I haven't even bothered looking).
In the end it seems more of a question of which bothers you more:
1. degraded sound quality and drastically shorter (since one is unlimited) battery life or
2. having a wire from your headphones to your audio source.
For me, there's no question that 1. is more of an issue, for others, 2. is a bigger problem. I consider bluetooth an alternative to wired headphones but absolutely not a replacement since both have tradeoffs
I think an apt analogy for the transition towards wireless audio is that of desktop to mobile computing. In the same way that mobile isn't an end-all to desktop computing for professionals, wireless headphones aren't meant as a replacement for everyone, such as audiophiles.
That said, I've personally tried a half-dozen wireless headphones over the past few months. I strongly feel that the technology has progressed to where the tradeoffs of battery life and sound quality are minimal for the general consumer.
Right now, price is probably the limiting factor in adoption. However, as the price decreases over the next 3 years, I think you'll find that wireless will become the primary means of audio consumption for the average Joe.
In the end it seems more of a question of which bothers you more:
1. degraded sound quality and drastically shorter (since one is unlimited) battery life or
2. having a wire from your headphones to your audio source.
For me, there's no question that 1. is more of an issue, for others, 2. is a bigger problem. I consider bluetooth an alternative to wired headphones but absolutely not a replacement since both have tradeoffs