Where did you get information that 319's were heading to Scotland?
Scotrail 385 windscreen issue will take 12 months to correct. 319s should be heading to Scotland asap. 380s being drafted across to Edinburgh route until 385s ready. 318, 319, 320 for Ayrshire and Inverclyde. 380 Ayr to Edinburgh and North Berwick through route curtailed temporary will only go to Glasgow.
314s may stay for another 2 years.
All speculation at this stage.
The only pretty much confirmed part of that is that the 385s look to be delayed up to the December 2019 timetable change and probably can see the 314s staying longer.
The 319s are not going to Scotland. Indeed, given recent announcements, there are actually going to be very few available! All 319/4s now spoken for, 11 for Northern, 19 for GWR, 5 for Wales and 5 at WMR. Two 319/3s in store, along with 18 319/0 and 319/2s, but 8 of these are reported as joining WMR - 319012/220 moved to Wolverton as a result and seems 319215 has now joined them, all presumably for reinstatement for WMR. 365s for the E&G seems to be the preferred patch up for now, along with 380s and apparently, the first HST may be deployed there from the May TT change this year. Current plans are very much fluid, a real mess...