The result can be magical if two seemingly good pairs are broken and a new pair is created (the reasons and circumstances were quite different in most cases), like
Volosozhar- Morozov and Mukhartova-Trankov were split to create Volosohar-Trankov. Result: World silver
Petrova-Sikharulidze and Berezhnaya-Shliakov were broken and the magical pair Berezhnaya-Sikharulidze was formed. Result: 2 world championships and an OGM
Stiegler-Zimmerman and Ina-Dungjen were broken to form Ina-Zimmerman, who had much more success.
In the USA there are a lot of 'musical pairs'- changing partners. Not all have had success.
Meno-Wentland(sp?) and Kuchiki-Sand were broken to form Meno&Sand who won a world silver and a couple of world bronzes (Kuchiki & Sand had also won two world bronzes)
Jamie Sale and her former partner (his name eludes me) skated in the 1994 Olympics. I don't know who Pelletier's partner was before he paired up with Jamie, but that was another very successful pair.
The other partner was not always successful, e.g. Kuchiki and Wentland- their pairs careers ended at that point. Mukhartova is in danger too. Dungjen turned pro and started skating with his wife Yuka Sato, but his eligible career ended at that point.
Occasionally the opposite can happen too. Obertas had much more success with the partner she left (I forgot his name) to skate with Slavnov,and their lack of success was not entirely Slavnov's fault.