Nazirv, you should be fine as long as your application is mostly complete and is paid for. If you've already sent it in, that's even better. I say "should be" but it is always up to the discretion of the officer at the border. They have the option of letting visitors in or not. It's a judgement call.
You imply that "[we] are permanently moving to Canada." You need to keep in mind that only you are permanently moving to Canada. Your wife (at least for the time being) is only visiting you.
The border officer must feel confident that your wife is not permanently moving at this time and that she will indeed return to the U.S. at the end of this visit (unless the PR is approved and then she may not have to). The officer has to be sure that she has the means to return to her home in the U.S. and that she is willing to do so (should the PR the refused for any reason). At minimum, she needs to have a place in the U.S. to call home. The officer also has to have assurances that your wife will not be tempted to work in Canada during her visit. Proof that you are able to support her and assurance that you will are probably called for.
They also want to be sure that she still has significant ties to the U.S. Probably her ties to the U.S. should be stronger than her ties to you. Needless to say, this is difficult to claim.
All that being said, once an inland application is underway, they are urged by the manuals to give permission to a sponsored visitor to remain visiting for as long as they think the application process will take, and if that Visitor Record expires they will normally extend it until you get a yes or no on the PR, as long as you continue to follow all the conditions on your stay.
