We are not in a hurry to implement this, due to more highly requested items. We do have plans to do it eventually though, and the default option would be not to update automatically. The preferred method would be to click a button to upgrade.
In terms of automation, there would be some options.
[x] Never update automatically
[ ] Security patches only
[ ] Patches only (including security)
[ ] Minor releases (including patches)
[ ] Major releases (including minor releases and patches)
[ ] BETA RELEASES (AT YOUR OWN RISK)
Something like that.