Even if you hold down
The worst thing is that can't turn the Mac off or restart. I get the message that I can't shut down because trash is being deleted.
Have you tried pressing and holding the start button? (Admittedly, that's not riskless.)
If you can shut down (or at least interrupt the hang) try emptying trash by control clicking on the trash dock icon then pressing and holding the option key before hitting Empty Trash.
I have the same problem. Both Force Empty Trash and via Terminal both just sit there.
As for the never-ending Trash? You can force quit/relaunch Finder.app and it stops.
EDIT: I opened up the Package Contents and tore into it, deleting items one by one. It might have something to do with the Text Styles folder. That was the final one that wouldn't empty out in Trash. I got rid of it finally by trashing the contents of Text Styles, then the directory itself, then the final Directory within the app. Good luck!
I was finally able to delete Motion with the help of a friendly Apple Support fellow here in Germany. It was a bit over a couple of weeks ago, but I can't precisely remember what we did, I'm sorry. From what I recall, it had something to do with external drives and other trashes. When we disconnected them all, including the Time Capsule, I think we were able to delete the app on the Mac. We might also have had to boot the Mac on root and, from there, go fish out the reluctant app with Terminal. Sorry, I should have written down what we did. Hope this helps.