I wouldn't be surprised if Nokia drops Gecko in favor of Webkit. The fact that Gecko is always loaded in memory in Maemo <= 5 so the browser starts faster is not the most desirable situation in a limited resource environment as a mobile phone. Also, Gecko has it's own toolkit so it doesn't fit with the rest of the desktop. If you want Gecko, installing Fennec should do the job.

ITOH I'm willing what is Nokia going to do for the Qt-ified Modest as it needs an HTML widget with DOM capabilities accesible through his API and AFAIK Qt Webkit lacks this support.