The forum software itself would more or less be upgraded in the same way 1.x upgrades are done - upload the files, run the script.
Any add-ons you install now will need to be rewritten by the authors and the upgrade process for them will depend on the add-on/author - some may just be able to be upgraded, some may need to be uninstalled and reinstalled.
If it is released in your 1 year period, it's simply downloading it. As for the add-ons (paid) that will be dependent on those developers whether there will be an upgrade fee associated with the 2.0 compatible version or not. For the free ones, you will have to wait until (and if) they release a 2.0 compatible version.
As for process.. it's no different than any current upgrade with the exception you "may" have to remove some of the 1.x line add-ons then reinstall them unless those developers have an upgrade path available also.