We don't know yet if we release it right away or if we wait for iwebkit 5 which we are already developing with lotof awsome stuff if it works out! We would also add other details beside form support. I'll talk with johan on why we will do.
Thank you for the update! It would nice to have the toggle button available before version 5 as I think developers using iwebkit would love to replace the html checkbox. A html checkbox doesn't really look right at the moment!
I'm looking forward in seeing version 5 in the future!