Apparently it won't ... first oportunity to try loading North America NT 2013.3 and the message is 'This is not supported by my device (2610)'
The 2610 uses pre NT mapping, hence the suggestion to use
OpenStreetMap data which will work with the 2610.
OpenStreetMap is peer generated open source mapping. In terms of coverage it's as good as the current Garmin mapping in most areas and better in quite a few. It's, generally, up to date as it can be and again usually better than the Garmin data. Route calculation may vary as the road attributes will be different, that doesn't mean worse... just different. It does lack some road attributes in comparison, for example there won't be speed limit data but that's not relevant on the 2610 anyway. There are plenty of POI included in the data as well.
The site linked to above provides both mapping for your GPS and to install in Basecamp or Mapsource. The mapping is far bigger than the mapping you already have in terms of MB/sq mile as it has far more data. It'll also be bigger than the current NT mapping as the latter is a compressed format. This means that you won't be able to fit all, or even half, of Europe onto a 2GB CF card (max size for 2610) but you should be able to fit sufficient on for all but the most ambitious of tours.
Another big plus is that there are no unlocking shenanigans, just install and go
I seriously suggest that you give it a try, especially if you're fond of saving a few bob...
After the 2610 came the 2720 and 2820, both outwardly similar in appearance but running NT mapping and quite a few features not found on the 2610. I have a 2720 that's waiting to go on eBay ATM
