10 digit phone numbers... Is that enough for USA?

My app may be used anywhere in the USA, but will be used by local businesses serving their own areas. As my project-in-development exists now (and I can change it) I'm storing only 10 digits. I'd like to think my software may be in use 10 years from now, although I can certainly release updates. But since the trend is for every person to have a phone instead of just one number per household, I understand the USA is running out of 10-digit phone numbers. I know it may not seem so, but yes, I HAVE Googled and the answer I seek is still as clear as mud. I read that there are locales within the USA (I don't know where) in which even within the same area code, a 1 and the area code must be dialed first. Other times, just the area code must be dialed, without the 1, even within the same area code. MY QUESTION IS: To accommodate the whole USA and the foreseeable future, will I need to add an "optional 1" in front of the number, in the form of a check box or other device to distinguish those which need a 1 from those that don't? Is there another phone number schema coming in the future? Or putting it all more simply: Is 10 digits enough?