The analysis is deeply flawed - historical results are not always good predictors of future performance - look at McLaren from 2008 to 2009, 2009 to 2010, Ferrari (likewise) and from 2010 to 2011, Honda to Brawn, Brawn to Mercedes W01, RB from 2010 to 2011 / 2011 to 2012, Lotus from 2011 to 2012, etc.
Teams move up and down, and tend to do so even more if their previous car was deeply flawed, which was the case of McLaren / Ferrari in 2009, and Mercedes in 2012.
Using past performance to predict future performance is very, very narrow-minded.
Using past performance as an indicator, please tell me where Marussia and Caterham will finish this season. I expect you'll say the bottom 2, and almost surely, you'll be right. What would you be basing that on? At least partly on past performance. And, again, you'd be right.
The changes you mention in your first para are instructive, but for the most part the "movements" (from "bad" car to "good" car) netted the teams a single place in the CC, in spite of VAST improvements to the cars. A change and an improvement - but the same change would see the Mercedes finishing 4th this year.
Honda/Brawn/Mercedes? Not a valid comparison - Honda to Brawn saw the change of an engine supplier and the Brawn benefitted from a clever interpretation of the rules; and it was the end of that ability to exploit that clever interpretation of the rules that saw the new "mercedes" team fail to equal the success that the Brawn had.
Major changes in fortune in F1 are generally caused by one of three things; changes in rules (for instance, Brawn in 2009 with their diffuser interpretation, or Ferrari's "fall" in 2005 due [at least in part] to changes in tyre regs), supplier changes (1988 - emergence of McLaren as totally dominant with Honda engine - previous dominant Honda engine user Williams slips to an irrelevant 7th with their new "Judd, or later, after Honda pulled out, McLaren's "erosion from form" with Ford and Peugeot before picking up the Mercedes...) or finally, and most rarely, personnel change; (Red Bull adding Adrian Newey).
Certainly Mercedes addition of Hamilton should be a benefit to them, and it is possible that the additions they have made with Lauda, Wolff and Costa may help, but I don't think that you would argue that these last three are anywhere near as transformative as Newey...
No - I'm not dooming Mercedes in 5th place for 2013 because that's where they were last year. I'm simply saying that, even in they sort out everything that was wrong with their car last season, this does not necessarily mean that they will automatically have the best car on the track, and it is not as if all the other teams have been standing around the water cooler all off season waiting for Mercedes to catch up. Given the lack of major rules changes, the stasis in suppliers and the too-recent additions to the "new-look" Mercedes team, I find it difficult to believe that they will make a "quantum"leap - that would be much more likely to happen next year.
Of course, this is all merely my opinion, and I could be fantastically wrong - we'll know in a couple of months....