I'm not worried about the promo, actually. Rihanna's free for the first quarter of 2014 for all we know. Rihanna respects her peers and loves Shakira, she would want this song to be successful and if Shakira calls her for a performance, Rihanna would never let her down.
Back at the 2010 VMAs, Rihanna wasn't planning to attend because she was snubbed. About 5 hours before the show, Eminem called her saying that performing the song without her wouldn't be the same and he wants her to be with him, so she took a private jet and flew to the VMAs just to perform with him.
I just hope the song is good
Everything else is settled, the song just has to catch up with the public. The streaming, radio play, digital sales, promo, etc. It just has to be good