Actually there's a lot of support for the idea, the only problem is none of it is from GameFreak so until they say it is/isn't based on Norse mythology, nothing can be proven right or wrong.
They've only confirmed Gogoat and Rhyhorn, but I did see the Strategy Guide have a section on riding Pokemon, so yeah hopefully we'll be able to ride lots of Pokemon! (Please let me ride Arcanine GameFreak )
That's all true, and everyone points the other way, but I shall stay hopeful! There's the whole "Special-based' Eeveelutions, how Eeveelutions are released in pairs, how the pairs have one type weak to the other, etc. But that's just me trying to spark a fire in heavy rain I guess :/
Does anyone know if the Sylveon movie short has been released yet? I was hoping because they never showed a "problem" in the trailer (Like how they showed Genesect destroying the city in the 16th Movie) that it was a secret antagonist, tad dah ! Dragon Eevee vs. Sylveon! ... Though if the movies already out then...damn
Xerneas being the Life pokemon puts it closer to the japanese myth of the guardian that protects the forest and Yveltal being the destruction Pokemon puts it closer to being a Yatagarasu which is a symbol of death and destruction. The unnamed eagle in norse myth plays no major role as far as destruction is concerned, and none of the four deer that live on yggdrasil symbolize life. There really isn't any concrete defense for the norse idea.
As for eevee, they are not always released in pairs, the very first release was a set of three. Being done twice after that has no standing as a truth. Special typing was already confirmed a false when Sylveon was released as Fairy Type. All marketing for Sylveon says she is the only new evolution. As for the Sylveon short, it airs right begore the Genesect movie. So yes its out. No one has made any comments about it but it plays right before the genesect movie in theaters.