It is in the interests of the US, and all civilized people, for Assad and Russia to regain total control over the entirety of the Syrian territory.
If Turkey invades, I would support the Russian Air Force taking out all their armor and troop concentrations.
Its not a question of if, but rather how long Turkey will remain in Syria.
A lot depends on how quickly the Kurdish fighters bend the knee to the Syrian government, something they should have done a year ago.
There will be no independent Kurdistan in Syria.