Funny thread! 

funny but sad as well...

I am exclusive contributor in last 12 months.
In last 12 months the number of images is doubled in my portfolio.
My income at iStock&Getty in just 70% higher than I was non-exclusive contributor. 

If I knew it would be so, I would never quit other sites and take exclusivity.

I think if you'd posted about your intentions beforehand, you'd have been advised to think extremely carefully before jumping into exclusivity (disclosure: I'm exclusive, but I've never been any other micro, don't fancy them, and don't even upload there any more.)
Not only are things going downhill there, but once you're exclusive your files are 3x more expensive than those of independents, so you have to consider whether your files are 3x that good; the promised boost in search placement doesn't always happen; and buyers can choose to buy a subs package which excludes signature files altogether.

I'll wait for another year, so I'll decide what to do next.

That's a lot of patience.  iStock does not pull enough weight on the market to consider it even casually as an exclusive distributor, and it's not going to improve. Plus buyers shop around, so raised prices work against you.

They know they are in decline and they are very nervous. In fact that's the only agency in my experience that could write an angry answer to a very simple and friendly technical question. I sympathize poor front line workers who are not sure about their future but why prop them? They can be used for the time being but they are going to bite the dust sooner or later. Exclusivity? Heck no.

So many of us have left istock now, I wouldn't be surprised if some people get more sales, as there's less competition....

Perhaps this phenomenon can be coined "the Istock Effect."