It's not totally unheard of, but I suspect progression while SVR is rare.
There's not a lot of citable studies easily found, but there was this:

http://www.hcvadvocate.org/news/newsLetter/2008/advocate0208.html#1

In this retrospective analysis, all 479 patients already had advanced fibrosis
or cirrhosis prior to initiating anti-viral therapy. Of that total, 142
achieved SVR. All patients were then followed for 5 years. Of the non-SVR
group (337 patients) 83 progressed to liver failure, HCC, and/or transplant.
Of the SVR group, only 4 patients progressed to one of those three outcomes (1
death, 3 HCC).

Considerations: the entire cohort was quite ill to begin with, and in the
synopsis referenced above there are no words concerning lifestyle (ie: drug
and/or alcohol abuse, etc) or co infection (with HIV, for example).

I would expect an even better result for folks who weren't already suffering
from such severe liver damage prior to treatment...

Cheers

/greyhackles