It depends on how you treat the battery and there is a big apparently random component too but 1 - 2% seems normal. A lot of the anticipation with respect to "b attery day" is centered on the hope that Tesla will be announcing a "million mile" battery, that is, one that has a useful lifetime of several thousand charge cycles as opposed to th ca 1000 cycles of today's batteries. Such a battery would, clearly, only lose a fraction of a percent per year.
Lithium Iron phosphate flavored lithium batteries basically are million mile batteries, though they have have less energy density.
Many other chemistry's have very high cycle life example: titanate flavored. Wiki says it has a 6k to 20k cycle life but less energy density, conversely the lithium air batteries seem to have insanely high density but horribly cycle life.
Tesla just has to figure out which one is the best for mass production, or best couple.
There's always trade offs, but personally I would rather have a bulkier or heavier battery for longer life of battery. but even with the new chemistrys, chemical batteries will always lose some life over time, 1-2% seems fair