Is it possible to export you card collection and deck composition into text format?
I'll update my response when we get additional information that's a bit more official.
In the mean time, according to the Scrolls Guide pseudo-official Scrolls Blog there is a mod update in the works for "a few weeks from now", which will hopefully translate into mid-July update.
From the very coy blog post, it looks like there will be a deck importation feature, as well as a previous match summary report. Hopefully if there is a deck importer, there is a deck exporter.
Knowing Mojang's track record and general friendliness to the external dev community, I'd reasonably speculate that if an export function exists, it will be in a text-readable format and will most likely be XML.
Summoner, the unofficial mod-loader from Scrolls Guide is out. (Get it here.) This mod allows for the import and export of deck information and is available for Windows and OS X.