I have the same question. I'm currently using a 2008 MBP, running Snow Leopard + Time Capsule. When the new iMacs come this month (fingers crossed

) I'll get one, running Mountain Lion. I know I could use a Thunderbolt connection between my old MBP and my new iMac, but I wonder if it wouldn't be even easier with the Time Capsule.
P.S.: if new iMacs don't arrive, I'll have the same question, but with a new MBP.