it would be only fair to state at announcement of the model
a) which features will be availible at Release
b) which features will be availible in EA
don't promise too much and then state "it is TBA". No, make a plan, stick to it (in terms of features and if possible in terms of time span of development). It is realy bad to have EA for years. EA should be max 3-6 months before final release.