I've recently added the security number enhancement device to my ebay password login. Can myibay snipe still place a bid if you don't have the current security device number, or will the snipe fail?

Short answer:
yes, it should work.

Long answer:
This feature was implemented and I used it personally some time ago.
I disabled it as it put extra load on the server, but nobody else seems to be using it anyway.
If you wish, please open a support ticket and I'll enable it for your account and explain how it works so you can use it.

Please provide your eBay user id by using this link:
http://www.myibay.com/login/contact