Yes. I bought a ticket once at Downtown Disney; they called into Visa, and issued me a card right then and there, and then I used it immediately to buy a ticket.
The ticket you buy now has no expiration until it is used for the first time, which in the case of a 1 day ticket, is the day of use. This is from the Disneyworld Website FAQS on tickets:
Q. Is there an expiration date on the tickets that I am ordering?
A. Our Magic Your Way Base Tickets expire 14 days from their first use. However, when you add the No Expiration Option to your ticket, you're free to come back and take advantage of unused days at any time in the future.