If the president is serious about changing NASA's current goal, he's going to have to make not just one speech about it, but many. He's going to have to visit the various NASA centers, he's going to have to show his personnal and steady commitment to it.

What I'm afraid could happen is the cancellation of the ISS (and the international commitments around it), the cancellation of the Shuttle flights, the cancellation of the unmanned interplanetary (not Mars or Moon related) projects, the pure science projects like space telescopes and the first start of the new NASA program but , because of its time and costs, its later cancellation too and nobody back in space at all, either in LEO or the Moon or naywhere else.
Even cancelling programs costs money and starting an entirely new one much much much more!

The first thing is to develope a new manned spacecraft, before the ISS or the Shuttle are grounded.
Then , perhaps, the program can continue through it.
A capsule can rely on different kinds of launchers, not just one, contrary to the Shuttle.
There are plenty of lessons to learn from the past. And from other countries.

Raoul