WebP is 2 years old by this point in time. Is there anything new that I missed?
But at its core, WebP hasn't been shown to be more than marginally better than JPEG, so why bother modifying your tool chain and work flow? You generally need something to be an order of magnitude better for people to bother.
When I was studying image compression back at university we wrote a whole bunch of lossy/lossless codecs. The issue is that most of the cool algorithms are protected by patents (such as Arithmetic coding). JPEG is quite old now and you can achieve much better results with wavelet coding as opposed to the traditional DCT approach. Plus it doesn't suffer the horrible blockiness effect that quantized DCT based stuff does.
Edit: If anybody has a few hours of time to waste here's a thesis I wrote on deblocking JPEG images a long time ago. http://www.csse.monash.edu.au/hons/projects/2005/Mirsad.Maka...
Isn't range coding widely viewed as being a legitimate workaround for the arithmetic coding patents? I guess in a year or two the question will be irrelevant, as the last of those patents will expire soon.
There's more here (though it's talking about video issues too): http://x264dev.multimedia.cx/archives/317
I think wavelets do have a future but it will just take more time and research. I'm not too sure what the state of it is at the moment as it has been a while since I've looked into it. It is my opinion that in time wavelet based compression will become more important though.
Edit: I forgot to mention that one really cool thing about wavelet codecs (for video especially) is that they are easy to scale by decoding portions of the bit stream. This is really useful for streaming as you can vary the image quality without too much work.