I expect interest rates to drift upward by a point or so by the end of 2010. But that's just a guess.
As for your deeper question--what will happen to the market when rates inevitably rise--that'll be a problem. Not primarily due to folks who've gotten conditioned to 5%-6% rates, though that is a factor. But just because every time rates rise, it makes properties makes properties more "expensive" by increasing the monthly mortgage payment. And the other tools that can be used to relieve that pressure (less money down, longer mortgages, ARMs) are either already in place or are unlikely to be used or expanded. FHA loans have become the new subprime loans for buyers with little money down. We already have ARMs. And I doubt that 50-year mortgages have much of a future.
To some extent, people will adjust. Back in 1984, gas prices averaged $1.21. See http://www.1980sflashback.com/1984/Economy.asp
Folks have gotten pretty used to paying $2.65 or so per gallon. See http://gasbuddy.com/
Beyond that, when interest rates raise, some people get squeezed out of the market. That's not necessarily a bad thing. Everyone should have the right to buy a home but, realistically, not everyone is cut out to be a homeowner.
Further, when interest rates went up to 16% or so, people came up with a lot of creative ideas on how to buy property. And they turned to some techniques that weren't necessary when interest rates were lower (such as 8% back in 1974 when I bought my first home). There's equity sharing, lease-options, lease-purchases, contract for deed, owner financing, and so on.
Some agents tend to be short-sighted. I remember a few years ago most agent poo-pooed home staging. Homes didn't need to be staged; even cluttered, dirty homes sold. I remember how resistant agents were to techniques like lease-options, how strenuously they argued against them. But a few years ago, if you could fog up a mirror, you could get a mortgage. Today, more agents are open to that concept.
There are plenty of ways for sellers to sell their homes, and buyers to buy their homes. And that applies whether interest rates are at 5% or 16%. Agents should help their buyers and sellers adapt to the changing climate. (Yes, many of them do. But we're talking about more extreme situations than interest rates going up a point or so.)
So, while interest rates may well rise some in 2010, I don't think that has to be a major problem for real estate.