The tyres are definitely having a major impact on things at the moment, but the fact is that of the Michelin teams, Williams are running their 2003 car, and it's blasting merrily through its development cycle. This is why the leading Michelin team is no longer McLaren.
Of the remaining races, I rather expect Hungary to favour Ferrari, as they've always done well there. Monza could go either Ferrari or Williams' way, but I expect Williams to win out. Indianapolis is likely to be a Williams milk run, and Suzuka probably favouring Michael personally, rather than a given team.
Things are looking tight for the championship, but with Montoya's win and Ralf's 10-place penalty for Hungary, it's a three-way now between JPM, MS and KR, with KR being somewhat sidelined by a lack of development.