They are sentencing them now because they know that Meng Wanzhou will be extradited. If they do the sentencing after the extradition then it will be perceived as retribution for extradition.
It is 50/50 that Meng Wanzhou will be set free soon.
If the court decision goes against her, she will appeal and live in her mansion in Vancouver while the appeals go through the court system, and knowing it could be stopped at any time depending on what the government could do.
That could be a long time. From her detention at Vancouver airport to now, that is already over 2½ years.