On the product page the "Skavenblight threat" battle pack is labeled as containing cards 1-20 of the Corruption cycle . A linked expansion series.

Any speculation as to if this will be a way of telling what types of cards are available within a given battle pack (I.E. Skaven and Witch Hunters)

Or, may this be a way of separating packs into legal sets... Such as type 2/standard in Magic.

Maybe it is both...

Let us look at its cousin AGoT for comparison.

For the AGoT LCG we have 2 finished cycles and 1 ongoing cycle of AGoT chapter packs available at this point:

A Clash of Arms (2008): a CP cycle containing a lot battle.

A Time of Ravens (2008): a CP cycle introducing the seasons mechanic for the first time...where ravens can change the seasons.

King's Landing (2009): a CP cycle thematically revolving around King's Landing (a location of political significance in Westros) and introduces the shadows mechanic (where you got cards entering and leaving a separate area) for the first time.

These cycle titles serves to both designate their identities as well as giving us some hint as to what we can hope to expect from them.

*NOTE: since there are no rotation as of yet, all cards in the LCG cycles are legal for LCG play so far. There is another supported format called Classic format (cards from CCG era are made legal for play but in a limited highlander fashion) and fan supported Standard format in AGoT, but that does not apply here for Invasion.

So far, the plans AFAIK are to not have any sort of 'rotation' with the LCGs. I could imagine this happening 2 years down the line, but for now, its just a thematic block of card's in a release.