No, multithreading not that simple - usually it's the last trick you should try to pull and even then only if the stars align just right.
You need to have expert programmers on hand (of the rare breed who can pull this off), the good luck to succeed and the time budget to spend on the big code reachitecting and experimentation.
If you're running on something else than modern consoles, you don't know how many cores your users will have, the average might be 2 so your average returns on the effort will suck (vs spending equivalent effort elsewhere).
Witness modern Web browsers, for example, where Google, Mozilla, Apple and Microsoft employ some of the best C++ programmers in the world, routinely of pulling off heroic feats, and they haven't seen it worth the effort yet despite Core 2 and Athlon X2 hitting mainstream desktop at about 2005-2006, 8 years ago.