But if you're gonna invest in lenses w an aps-c, might make sense to invest in ff lenses so you can use on ff as well. The use of each lense may be different w the crop factor.
If you eventually upgrade to a full-frame you probably won't be going with Sony anyway, as there's not much room to expand your collection, as would be the case with, say, Nikon or Canon. So not much point in spending extra for the full-frame version, unless you know that specifically that you'll be expanding within that set.