It might not be Theme Park as you remember it, as E.A. Tokyo are the developers. I’m not sure which studio is developing Boku To Sim No Machi+, the new Sims game for the DS [E.A. Japan is the only name I have seen attached], but they have definitely changed The Sims. It now has a distinct Animal Crossing style in artwork, and possibly a small similarity in gameplay too.
Having said that, it looks almost identical. Perhaps the best piece of news here is that good sales would encourage, say, Chris Sawyer or Frontier to release a version of their games on the DS.
+Apologies for using the Japanese name. I don’t know how it translates, and there is already a Sims game on the DS.