Remember that the "simple" release strategy will only look at the metadata (typically size). So the optimized aggregator won't be able to use the `SAMG`.

Actually, I see SimpleMessageGroup always returns true so I suppose it can simply not do the canAdd() call in this optimized version.

Another alternative would be for the new release strategy takes 2 args

    canRelease(metaBeforeAdding, newMessage);

If we decide we need a new method on meta (or even the store), we can always subclass in 4.0 and merge in 4.1.