So does this mean that Twitter development is done, and devs will just move elsewhere? No way. Devs go where the customers are, and the customers are using Twitter in increasing numbers. I do development as a business and as a businessman, I go where the money is. That is still Twitter.
The reality is that adapting to version 1.1 is not a big deal. The real change for client-side developers is that they will have to call their server with the API request, and let it call Twitter and return the results. In the end, the JS code is still making an Ajax request to a server and getting back JSON. The only difference will be that the server they call is one they control instead of calling Twitter’s API servers. Not a huge difference. Not enough to make devs leave all these users behind or give up coding.