Well I think that Mr. Knopfler cannot stop writing, and from following him and the band(s) since the 80´ies, I think he would want to record those songs and put them on an album, and for sure take his time to do so.
I think that the reason we see the ATMOS and previously un-released tracks), is because MK has decided to give the people (fans) something else now that touring and live concerts are over and done. I dont think it is a complete coincidence that these releases pops out now.