As the title says.
At the moment they're getting well and truly flogged (howardj's "How can people think England won't win a Test" is looking particularly good as a prediction at present?) Obviously a whitewash would theoretically make them look the worst England side since the 1920s, but at the same time the competition isn't exactly great. In order of ICC rankings...
Pakistan: Their current side lacks Shoaib and Asif, and a side without Shoaib and Asif lost 2-0 in England. I think it's fair to say that it's at least even between the two, even if England should lose 4-0 or 5-0 (consider that the last Pak v Aus meeting ended 3-0) Without drugs...then maybe Pakistan is two, but England are also better with S Jones.
India: Perhaps, but they only managed 1-1 at home to England, and had three drawn Tests against West Indies. Away from home, their bowlers do not have a good record at all.
Sri Lanka: Managed a strong 1-1 series result in England, and beat South Africa 2-0 at home. Are currently carrying at least one bowler (Maharoof), though, and still need to develop Tharanga into a worthy heir to Atapattu. Also lost to India 0-2 about a year ago.
South Africa: Not good in the subcontinent, and fell 0-5 with one draw to Australia over the last summer, not exactly impressive. Couple of good bowlers in Ntini and Nel, and allrounders will help them draw a few.
New Zealand: Bond will no doubt break down before their next Test series, leaving them with a bunch of half-decent seamers like Franklin and Mills - just like they've always had, really. Brittle batting lineup which doesn't know who is supposed to play where. Also does not play Tests.
West Indies: Too many passengers - Ganga, Gayle, Morton/Sarwan, Edwards - to make a good Test side. Bravo isn't a consistent performer yet either. Nil away Test wins in their last 35 attempts against decent opposition.
In other words...even if you retired Ponting, Hussey, McGrath, Warne, Gilchrist and Hayden right now, I think Australia would pretty much be world No. 1. Yet this Aussie side is a fair bit worse than the one five years ago (or is it?) suggesting that Test cricket, in general, is "going through a transitional period" (the euphemism for "the new players are dire")