Upload & Sell: On
People are attracted to the a7/a7r for all sorts of reasons. Already savvy users are mixing and matching - for instance, many will find the 55mm most appealing but need a 28mm or a fast 35mm or 90mm - so high quality, often low cost alts fill the gap very satisfyingly while Sony Zeiss gear up production for those who prefer AF and OEM. Telephoto users are discovering what setups quell the shutter action best. FD and OM and loads more lenses are pressed into service.
The 55mm is a bargain, best in its class and is being recognised as such, and there will be four lenses as of next week. I think the sales will be a slow burn deal, as more users realise they don't need many lenses for what they do, and get to see how excellent the FE lenses are, how liberating small cameras can be.
What proportion of users only ever need a good zoom and excellent body - 50%? How many M lenses does the average Leica M user own? The 'system' meme falls apart quickly when examined in any detail. How about single lens cameras - not much system there, but visit the RX1 images thread to see what they produce. AF is fast enough for most, FPS ditto.
The 24-70/4 is likely to be better than the DSLR equivalents, so why lug a 2kg rig when something half the weight/size does a better job? As stated, the 28-70 is already a fine choice and a bargain for something with 3 asph elements and an ED element. Both are very light for what they do.
File size and PCs...the A900 produced 36+ Mp files five years ago. Upgrade.