Trump need to be very careful with the arms of Rick, but tomorrow the militants. Today they can be friendly to America, but tomorrow, circumstances may change and they turn their weapons against the Americans.
Normally I'd agree seeing how the US have a hobby of creating and arming terrorist groups who later turn against them(Al-Quaeda), but I think the Kurds are more likely to turn against the Turks(actually they already have) so I'd say that's a pretty safe investment.
It will be interesting if after the war Kurds manage to negotiate the separation of Kurdistan from Syria. Such a development in either Syria or Iraq(or both) is very unwanted for Erdogan, as the creation of an independent Kurd state will most likely make the Turkish PKK even more aggressive in their campaign to separate Kurd populated areas from Turkey.