Not only is the rebate offer inadequate, but you must use it by April 20 even if you have to file an emended return later!

Here's their language. Be sure to read the last line:
To get $25 back from TurboTax, you'll need to have:
Filed your 2013 taxes using TurboTax Deluxe CD or download edition; and
Upgraded to TurboTax Premier or TurboTax Home & Business because of your tax situation; and
Filed your 2014 return (either e-file or mail) with TurboTax Premier or TurboTax Home & Business; and
Filed your return no later than April 20, 2015.
If you filed an extension or need to amend, your final or amended return must still be filed by April 20.