Considering The Sims 3 with all the expansions runs around $450......
I'm gonna go with yes.
As if that's even a drop in the bucket. Just the 7 DLC worlds on the store are over $220 if you get the gold versions. Then there's easily another $1000 in other store DLC, clothing, hair, furniture. Add stuff packs for another $200, and the $450 from expansions, and you have a single game that could cost you close to, if not more than, $2000 to "complete."
Expect the same for SimCity, if it succeeds. If it doesn't expect a total lack of content, support, or patches. See Darkspore, though at least the game is still online, sort of.
I imagine lots of buildings being released for SimCity, better parks, tourist attractions, utilities, etc. Not just stuff that changes how things looks, but actual gameplay effecting DLC you'll feel like you have to buy.