Well, personally I am a supporter of the “Sound/Sonic and Light” type theory. The theory suggests that both legondaries; Yveltal and Xerneas, are two new types to this generation. Yveltal being the Sound/Sonic type, and Xerneas being Light type.
Here is the most basic form of the Sound/Sonic and Light theory explained:
The theory also suggests that some Pokemon that are currently in the series would have their types altered/changed, or the new type added to their current type… Here is a picture of possible Pokemon that would most likely fit these two theory types:
Along with this theory (As well as many of the other supporters of this theory), I believe that if this theory is correct, Sylveon would be a Light type… My own theory I thought up when I first took a good look at the CoroCoro page when Slyveon was first announced, I came up with a thoery that might suggest that Slyveon is a Gender Exclusive evolution to Eevee (Specifically Female), and that there might be another Eeveelution to this generation that we have not yet seen, that could be Sound type, and Male Exclusive…
Would Gamefreak really change all of the types of those Pokemon to the new types? Probably not… But considering that when a new type was introduced in the past, Gamefreak did change two Pokemon to that type when it was brought in… Of course, I speak of Magnemite and Magneton, considering they were both Pure Electric prior to Gen 2…
The argument of “Pokemon is getting too confusing as it is. we don’t need anymore types…” to me is just silly… Sure, it can get a bit confusing at times, but what you are suggesting is to just leave the series as it is now with no new types since Gen 2… I think it would be quite interesting to get some new types, since the generation that I grew up with the most (Gen 2) was the first to ever introduce “New” types into the series, it would be great to see it happen again on my end… Not to mention, it would be nice to see where these new types fit in competitively~ Granted, that is if this theory ends up being true or not… I honestly wouldn’t be disappointed if it ended up not happening, but I would be quite glad if it did… So either way, I don’t really mind that much.
Well, all crack-pot theories aside… If I had to choose one type that isn’t a “New Type” that best fits Slyveon, I would probably say Flying… The whole “It’s a Normal Type” thing might be true, but it just seems so boring… Eevee is cool in the sense that it can evolve into soooo many things… Why all of a sudden would they want Eevee to evolve, yet retain it’s old typing? That is just kind of boring to me (But it could still happen -shrug-)
If it hasn’t become apparent yet, I LOOOVE Gen 6 already… I love all of the theories, I love that this is the first main-series Pokemon game that is being released internationally at the same date, I love all of the subtle hints and the hype, I love the designs of the current Pokemon we have seen… I can go on for a LONG time about how much I am hyped for Gen 6, which says sooo much for this generation to me… Considering that when Gen 5 was announced, I wasn’t too impressed by the Pokemon designs at first, and it took me a good while to get used to them (Granted, Gen 5 is now one of my favourite Pokemon generations~)
Well, Gen 6 is only half a year away, so we still have a short while to enjoy all of the theories, hype, and drama… Start rolling in it while you still can~