The only thing I can see happening to me is my phone becoming blacklisted. I don't know how long that will take. It could be a month from now or never.
I don't see how it would be even remotely possible for me to get a valid charge on my bill for a ~$57 insurance deductible and a $200+ charge for not returning a phone to Asurion though since I don't have insurance on my line. Never have, never will. My family has been a sprint customer for 7 years now and although we've had insurance on other lines, it has never been on my own. We share a family plan with 3 lines.
I'm still on the fence as to what I should do.