User blog comment:Besteverunited/Do you think after the tartarus arc there will be a break in the anime or is the new manga arc designed for this reason?/@comment-7418318-20150227083944/@comment-4829046-20150228060651

Uh.... The 1st light novel occurs after the Edolas arc in the main series anyway so putting it as a flashback works fine. The Light Novel did not contradict anything in Earthland after all. And the light novel was beautiful so animating it would be a smart move.