I'd say Keystone XL might not be as dead as people are saying. We both over estimated how much Trump's approval was worth, and how much a President can do to undo it after the fact, at least in the case of the border crossing. Sure, we won't get a new border crossing Presidential permit, but undoing an old one isn't as easy as signing an executive order, as the crossing is done.
The river crossings though, the pipeline needs to cross the Missouri River or major tributaries at least twice. When the court quashed permit 12 which changed the environmental liability and assessment requirement for building around rivers/wetlands, the Trump administration's attempts to speed up processes instead led to the processes being stopped (remind you of anything that happened in Canada?). Denying permits for river crossings when the proper process is followed isn't something the executive branch could do to only one project while letting similar ones go forward . They might be left with two options: end all new liquid pipelines that need federal permits, or allow Keystone XL.
I am not sure what the government would choose to do under those circumstances.