I just don't think Arsenal can be ruled out for 'x' number of years when an 'inexperienced' Arsenal team (2008) finished the same number of points behind Man Utd as Liverpool did last season. Sure they need a few additional players but you can't rule them out. I certainly don't see Liverpool achieving that points total again next season which in itself wouldn't have been enough to win the league in the last 6 years.
So if you think Liverpool cant do it again - what makes you think Arsenal can?
I think Arsenal will easily make the top four again, personally just think without major losses to all three teams above them, they cant compete over 38 games ( yes Utd have had a major loss in one sense, but the team as a whole should be stronger as long as SAF doesnt find another Veron / Djemba Djemba/ Kleberson, and imo Valencia will make a good addition even though not a direct replacement from goals point of view)