No, your colon can be affected by old age (diverticulosis, colon cancer), but IBD is - mostly - a young person's disease. There's always exceptions, but most folks get IBD for the first time in their late teens or 20s. It isn't a disease of aging unlike, say, diverticulosis which almost never appears before the age of 40 and becomes much more common after the age of 60.
But the process of aging has no effect on IBD. If anything, in theory, flares should become milder in old age because the immune system is weaker in old age. Whether that actually happens in practice or not, I have no idea.
I think you and soy are arguing two different things here. Disease onset and disease progression are not the same. It is pretty well established that Crohn's is a progressive disease, but I could not recall whether or not I had ever read anything that alluded to this in UC, although I just sort of assumed it was also progressive and would get worse with age. I stumbled across a clinical review from 2011 that argues that UC is, in fact, a progressive disease. Food for thought if you'd like to read through at some point. It's a bit long. There were some interesting tidbits of information in the article that I did not know. See link:onlinelibrary.wiley.com/doi/10.1002/ibd.22839/full
Male Mid 30's
Diagnosed Proctosigmoiditis (UC) February 2015
Current Meds: Lialda 1.2gm 2x daily, generic rowasa as needed
Perianal Abscess June 2015
Fistulotomy December 2015...Doc's still say it's UC, not Crohn's
Specific Carbohydrate Diet started June 2015. Still going strong.
"Happiness doesn't depend on who you are or what you have, it depends solely on what you think." -Dale Carnegie