I'm wondering the same thing. So not happy about this
I think the options are phone gap build (but that's ~$10/month for more than one app), or cocoon & Ludei , but I'm not sure how this is used. I see there's a tutorial, but it's rather dated, and I don't want to explore that until I know it's still relevant. Also, you have to send to Ludei and wait about 20 minutes for them to email you a file. Is that normal? 20 minutes is a long time.
XDK will be missed.