Thanks for the quick replies folks. Like I said, the stock mirrors on my 2003 are almost wide enough, but I suspect you're right that, though the 2015 may be better, they still won't be adequate. We've been using add-on mirrors on my 2003, and they're fine. I may just use them on the new one, but the optional tow mirrors would be nice. I'm not financing, but $600 extra on a new truck is not that much. I might even get them to give them to me to seal the deal ;)
Jeremiah, my trailer is under 5000 pounds, and my current Tundra handles pretty well, but it's at the upper end of it's tow capacity. The 2015, with the 5.7 liter V-8 and a tow package, has almost double the capacity, so I feel it'll be fine.
I'm a Toyota guy. If I were buying anything else, it'd probably be a Ford, and I may give one a look before committing.
Thanks again for the quick responses.