Yes, you will receive Denim, Microsoft says Q4 this year, but subject to carrier cooperation. Expect it by the end of the year, at least, for the first roll-out (it won't start by the 620 I guess).
It gives you a time frame, though, and nobody will be able to tell you more.
as first as I know yes, we will recieve denim update, but not all features will be available to lower end, like the rich capture /HDR, and its really sad, hdr is really great feautes in a camera phone
i dont mind if we dont receive HDR
we can always resort to apps/filters
im just hoping for a faster startup camera and improved quality
plus, i hope theyll support flash on burst shots