AppEngine: switching to Python 2.7
There is no way to avoid changing the app ID, but you can request that the old ID be aliased so requests to old_appid.appspot.com will be handled by the new application. If you're serving the application on your own domain, of course, the app ID is irrelevant.
The Master/Slave datastore will almost certainly never be supported on Python 2.7; Google doesn't recommend its use at all (I wouldn't use the term deprecated, since they've expressed no plans to actually remove it and kill the huge number of existing applications using it, but they certainly want to do as much as they can to discourage its use.)
For tons of reasons, I would like to go ahead and switch to Python 2.7. The new python version requires using the High Replication Datastore. As far as I can see, converting to it is not really possible: the only way is to create a new app, with new ID, and copy over the datastore. Changing my app ID is something I am not keen on doing.
Is there a way around App ID changing? Or is a workaround expected in the near future? Will the 2.7 version eventually support the Master/Slave Datastore? I suppose not all AppEngine users will be that happily changing their id...