I got an email recently asking me to register my cellphone with the Do Not Call list within 6 days because all the cellphone numbers will be released to telemarketers. It's false. No such deadline exists. In fact, this chain email bullshit has been going on for a while. You can register your cellphone - multiple phone numbers - any time here. FCC has also issued a warning re: this confusion. It is advised that you do register your cellphone because a good number of people have switched to using their cellphones as their primary phone and use them to fill out forms when opening accounts etc. But there is no deadline to do so. The other myth that has been circling around is your original registration will expire in 5 years; if you remember, the call to sign up was back in 2003. FTC has pledged to not drop numbers from the registry. The annual developments on this issue is available here.
Get all the details about the registry here.