For several reasons, the timeframe is hard to establish... 0.9.7 has been improved a lot from what originally in the feature list (ext 2.0 js, but also several features have been added) and also the "food on the table" factor has delayed the dev team from progressing as fast as it might have...
As far as the migration to 0.9.7 goes, don’t worry there will be a migration script and it’s already been put to test... the main item which will remain is converting addons to the new branch. Luckily the 0.9.7 API is well documented and the process should be as quick and seamless as possible
This being said, my advice would be the following : if the project is not urgent, you might wait till 0.9.7. But in most case, use 0.9.6.1 (and soon 0.9.6.2). If you need right now to push customization further, use 0.9.6.x along with xPDO. Any custom development you’ll work on based on xPDO should be fast to switch to 0.9.7 (which is based on xPDO).
I’ll let the dev/coding team refine this but this is what I understand of it...