Got a reply from my contact at Garmin:

Hi Luke,



There is an update planned to support the Nokia 5800 and we will make it available soon. We’re currently evaluating the market to determine if we will support the N97.

So good news.

Hmmmm... really never been that impressed with XT, so I'd be alot happier if ALK or TomTom were to announce they were going to support S60v5

I'll ask my ALK contact about that then, but it's pretty much certain Tomtom won't be.