I find it quite likely the 379s will find a home. Great Northern almost seems like an obvious place since the 387s don't run at 110mph and can be used elsewhere in the Southern network where they are needed, and the 379s are much more appropriate for the long distance services GN operate.
I suspect that Great Northern now isn't going to happen, despite being the original destination identified for the units. The 387s are working fine on the route and they have brought in the extra c2c units to get the desired fleet of 35 units.
I suspect it is also likely that the 379s would have lost their current first class area if they had found a use. That will change the view on whether they are better suited to long distance services.
Scrap is definitely possible for the 379s because they aren't needed.
But then I was amazed they went for 360s rather than 379s. Cost I guess.
The fleet size of 21 360s is perfect for EMR and gave a 'blank canvas' on which to install a different interior. Meanwhile, the 379s were almost certainly destined for the Great Northern routes, to replace 387s and work alongside 365s. History can't be changed.
What has changed is that the 387s aren't needed at Southern so they have stayed at Great Northern and the rolling stock plan has been changed to require fewer units on both the Southern and Great Northern operations.
Moreover, the 360s haven't received a new interior, but it doesn't mean that it wasn't originally planned that would be the case.