No, not with encrypted-locked bootloaders becoming common. For Verizon starting with the Samsung Galaxy S3 and phones after that era, and AT&T with the Samsung Galaxy S4 and other phones, you will have tough time putting anything other than what the carrier supports. You may get lucky and be able to break it, but it takes a lot longer. If there are unlocked bootloaders available, you may be able take matters into your own hands, but it is quite risky.
Also, when you buy a phone locked to a carrier, you may not be getting what's advertised elsewhere. iPhones are universal, Android, not so much. The AT&T Galaxy S3 (i747) was completely different than the international S3 (i9300). Some things were better - more RAM (2GB vs 1GB), slightly faster processor (1.5 GHz vs 1.4GHz), and faster cellular data (4G LTE vs 3G). Others things weren't so good - dual core instead of quad core (Snapdragon S4+ 'Krait' vs ARM Cortex-A9), weaker graphics processor (Adreno 225 vs ARM Mali 400), less storage (16GB vs 32GB), and a lot less battery time. And a broken GPS, if you upgrade to KitKat - even on stock. I wouldn't recommend buying a locked carrier phone (other than an iPhone) for anyone.